Low Suction Research Articles

Probabilistic Analysis of Highly Nonlinear Models by Adaptive Sparse Polynomial Chaos: Transient Infiltration in Unsaturated Soil

Polynomial chaos expansion (PCE) is widely adopted in geotechnical engineering as a surrogate model for probabilistic analysis. However, the traditional low-order PCE may be unfeasible for unsaturated transient-state models due to the high nonlinearity. In this study, a temporal-spatial surrogate model of adaptive sparse polynomial chaos expansions (AS-PCE) is established based on hyperbolic truncation with stepwise regression as surrogate models to improve computational efficiency. The uncertainty of pore water pressure of an unsaturated slope under transient-state rainfall infiltration considering hydraulic spatial variability is studied. The saturated coefficient of permeability [Formula: see text] is chosen to be spatial variability to account for the soil hydraulic uncertainty. The effects of location and time and the performances of AS-PCE are investigated. As rainfall goes on, the range of the pore pressure head becomes larger and the spatial variability of [Formula: see text] has little influence in the unsaturated zone with high matric suction. The pore pressure head under the water table suffers more uncertainty than it in the unsaturated zone. The [Formula: see text] in the high matric suction zone has a trend of rising first and then falling. Except for the high matric suction zone, the [Formula: see text] rise over time and they are almost 1 at the end of the time. It can be concluded that the AS-PCE performs better for low matric suction and positive pore pressure head and the fitting effect gradually increases as the rainfall progresses. The quartiles and at least up to second statistical moments can be characterized by the AS-PCE for transient infiltration in unsaturated soil slopes under rainfall.

The unsaturated seepage process and mechanism of internal interfaces in loess-filled slopes during intermittent rainfall

In the “Gully Land Reclamation” project conducted in Yan’an, China, shallow failure in the middle of loess-filled slopes is caused by the unsaturated seepage of rainwater along the internal interface between the original loess slopes and the loess-filled slopes. Although the phenomenon was observed through model test, the particular nature of the unsaturated seepage mechanism remains unclear. To explore this mechanism, we carried out an intermittent rainfall model test on a loess-filled slope, and the volume water content in different areas was continuously monitored. Based on the monitored data, the unsaturated seepage process and mechanism in the internal interface was analyzed by adopting the Fredlund and Xing model and the Childs and Collis-Geroge model. The results indicate that a water accumulation phenome occurs in the middle area of loess-filled slope because of low matric suction in the middle area and high matric suction in the bottom area. In addition, the dynamic process of pore growth and shrinkage at different areas prevents seepage to the bottom area. Furthermore, the regularity of pores at the interface during intermittent rainfall is summarized from a macroscopic perspective based on the matric suction and permeability coefficient. The unsaturated seepage process and mechanism affected by Knudsen diffusion are revealed. Because of the presence of unsaturated seepage, a shallow failure appears in the middle area of a loess-filled slope. The results have a significant impact on the field applications of interfacial impermeable prevention measures.

Evaluation of Soil-Water Characteristic Curves for Different Textural Soils Using Fractal Analysis

The soil-water characteristic curve (SWCC) is an essential tool to determine hydraulic and mechanical properties of unsaturated soils. As an inherent influencing factor, soil texture controls the characteristics of SWCCs. Fractal theory can quantitatively describe the physical characteristics of soil. This study used particle size distribution data and water content data contained in the UNSODA2.0 database to explore the fractal characteristics of 12 soil types with different textures under different matrix suctions. The SWCC fractal model was adopted to characterize the hydraulic properties of soil with various soil textures. The findings revealed that the mass fractal dimensions of particles from these 12 different soil types significantly differed and were closely related to the clay content. Fractal dimension increased with increasing clay content. The fractal dimension established a good relationship between soil structure and hydraulic properties. Fractal analysis can be used to determine the connection between physical properties and soil hydraulic parameters. The estimated results of the SWCC fractal model indicated that it had a good performance regarding the description of SWCCs for the 12 soil textures. The soil structure could be described through fractal dimensions, which can effectively indicate soil hydraulic characteristics. The estimated fractal dimension of this model could be obtained by particle size distribution. Furthermore, using the SWCC fractal model, we found that the SWCC of coarse textured soil changed sharply in the low suction stage and its residual water content was small, and the SWCC of fine textured soil changed gently with a large residual water content. The water retention capacity followed the order clay > silty clay > sandy clay > clay loam > silty clay loam > sandy clay loam > loam > silt loam > sandy loam > silt > loamy sand > sand.

Quantifying Coupling Effects Between Soil Matric Potential and Osmotic Potential

AbstractSoil matric potential and osmotic potential are widely accepted as two independent components of total soil water potential. However, laboratory observations repeatedly demonstrated that matric potential can vary with salt concentration, implying a potential coupling between matric potential and osmotic potential. To date, it remains elusive whether matric potential and osmotic potential are independent or not and why so, and a theoretical theory for quantifying the coupling between them is still missing. Herein, a theoretical model is developed to quantitatively explain this problem via a lens provided by a recent concept of soil sorptive potential (SSP). The proposed model substantiates that matric potential and osmotic potential are not independent. The increasing salt concentration can notably depress two variables underpinning SSP, namely relative permittivity and electrical double layer thickness, leading to non‐negligible decreasing (more negative) of matric potential in the high suction range, and increasing (less negative) of it in the low suction range. In turn, the soil‐water interactions redistribute ions in soil water, raising osmotic potential especially for clay with high cation exchange capacity. The proposed model shows excellent performance in capturing experimental data, validating its accuracy. A parametric study implies that the neglection of coupling effects can lead to a significant underestimation of soil hydraulic conductivity in the film flow regime.

Soil–water characteristic curve of unsaturated collapsible soils

AbstractCollapsible soils are almost found in unsaturated states and involved significant engineering problems. Geotechnical challenges of such soils are represented by the hydro-mechanical behaviour during wetting–drying cycles due to the humidity and climate conditions. The main objective of this paper is to investigate the soil–water characteristic curve (SWCC) of unsaturated collapsible soils. In this study, three types of collapsible soils were investigated such as natural soils of sandy gypseous, silty loess, and artificial soil of gypsum–sand mixture. Determination of soil–water characteristic curve represented by wetting and drying paths has been done using a combination of the axis-translation technique (i.e. pressure plate device) and vapour equilibrium technique (i.e. salts solution desiccators) to cover a wide range of applied suction. The test results show that the air-entry value for all soils occurs at a very low suction range. At the boundary effect zone, the coarse grain size of the soil mass cannot hold the water molecules in the pore space, even with a low value of imposed suction. Moreover, the amount of hysteresis varied based on the geological formation and homogeneity of the soil fabric. Furthermore, SWCC has been interpreted by insignificant volume change and a slight reduction in void ratio, especially at high applied suction.

Evaluation of climate change on the collapse potential of unsaturated cement-treated laterite soil for disaster risk reduction

Extreme weather events and intense rainfall may alter the climate, which would probably affect the geotechnical constructions such as unsaturated embankments. Basically, soil moisture content determines the strength of the unsaturated soil, with wetter soils often being weaker. Although it has been proved that unsaturated condition substantially impacts the shear strength and volumetric behaviour of soil, its implications are rarely investigated or taken into account in the design. As a result, changes in temperature and rainfall loads will have an influence on geotechnical constructions and develop long-term seasonal deformations that might severely jeopardize safety and maintenance. Therefore, it is crucial to assess the effects of the climate on soil behaviour for each location through adequate geotechnical laboratory tests. Johor, Malaysia has a large area and abundant tropical soils. Hence, this study aimed to elucidate the influence of climate change on soil behaviour in the tropical regions of Johor. To impose Malaysia's climate, a series of modified suction-controlled oedometer tests are conducted under different matric suctions. The outcomes revealed that the low and high matric suction has significantly impacted the untreated and cementtreated soil. However, the great reduction of soil settlement is mostly from the coupling effect of saturation and stabiliser.

Effect of Hydro-Mechanical Hysteresis on Active Earth Pressure for Unsaturated Soils

Stability analysis of retaining structures carried out at unsaturated conditions mainly dismissed the effect of hydraulic and mechanical hysteresis on the exerted active thrust. This paper reports a parametric study into the influence of hydraulic and mechanical hysteresis as well as soil types on active earth pressure carried out at low and high suction profiles to envision the pattern of the exerted active thrust for various simulated soils, from sands to clays. Generally, the numerical results exhibited a non-linear relationship between active thrust and suction. The influence of hydraulic and mechanical hysteresis and soil types on the active thrust was seen very significant. A reduction inPaof 1.62 fold ats= 137.34 kPa, owing to the influence of hydraulic and mechanical hysteresis, was obtained when comparing two simulated soils; silt and clay. A soil with a wider capillarity range showed a higher positive effect of the hydraulic and mechanical hysteresis on the exerted active thrust.

Large cell triaxial tests of a partially saturated soil with vegetation

The use of vegetation roots as a nature-based solution against landslides and erosion requires the definition of sample preparation protocols and adoption of equipment that allows testing representative elementary volumes of the whole soil-root system. For this purpose, large cell triaxial compression tests were carried out on fallow and vegetated samples at different degrees of saturation. Samples were prepared by static compaction of a silty sand and seeded with Cynodon dactylon. The hydraulic state during plants growth was controlled and reproduced on bare soil samples. After isotropic compressions, the shearing phase was carried out at very low confining stresses (i.e., below 50 kPa). Tests were deemed to be comparable by assessing the normalised volume of roots with respect to soil, after shearing. For a given confining stress, soil samples with higher matric suction exhibited higher shear strength, furtherly increased by roots. The stress-strain behaviour observed in the vegetated soil systematically changed, when comparing tests at low and high matric suction values, due to the different mechanisms of vegetation reinforcement depending on the hydraulic state at the soil-root interface. The results were successfully interpreted within a failure criterion and skeleton stress framework for partially saturated soils, considering soil suction, degree of saturation, soil microstructure and the normalised volume of roots.

Chest drainage outcomes by water seal versus low suction on digital drainage systems after lung resection: retrospective study

Chest drainage outcomes by water seal versus low suction on digital drainage systems after lung resection: retrospective study

Investigation into the compression behaviour of unsaturated damaged Callovo-Oxfordian claystone

In this study, the compression behaviour of unsaturated damaged COx claystone is investigated by performing high pressure oedometer tests with controlled suction. The damaged oedometer samples were prepared by shearing the claystone in triaxial conditions. Four high pressure oedometer tests were conducted using different controlled suctions. The effects of suction and damage on the swelling and compression were investigated in oedometer. Results show that the intact claystone exhibits a larger swelling strain than that of the damaged one at the same imposed suction. The damaged claystone at a lower suction displays a smaller yield stress and higher compressibility, and exhibits a larger compression index Cc than the intact one, evidencing the effect of damage. In addition, the step compression index Cc* increases with the increase of vertical stress, while deceases with the decrease of suction. This indicates the dependencies of compression behaviour on vertical stress and suction.

Investigations on the coupling principle of the four-stage DC linear compressor unit used in a hybrid cryocooler operating in 1–2 K

In a hybrid cryocooler developed for operating in 1–2 K, a four-stage DC linear compressor (DCLC) unit used in a Joule-Thomson cooler (JTC) is designed to provide the extremely low suction pressure of below 3.1 kPa. An equivalent non-linear dynamic model is proposed to analyze the gas spring force within the cylinder, and the coupling principles among stages of the DCLC unit are analyzed and summarized for the optimal design. In a standalone test platform, the experimental results show that the designed four-stage DCLC unit can provide a suction pressure of 2.1 kPa, for which a total pressure ratio (TPR) of 102.5 is reached with a pressure ratio loss (PRL) of 13.4%. Furthermore, in the actual hybrid cryocooler, the acquired values of suction pressure, TPR and PRL are 1.75 kPa, 101.7 and 14.1%, respectively, which is of great significance for the hybrid cryocooler in achieving 1.8 K. The rationality and feasibility of the coupling principle are experimentally verified.

Effect of compaction condition on the water retention capacity, microstructure and its evolution during drying of compacted loess

To investigate the initial microstructure and water retention capacity of compacted loess molded under different compaction energy, the soil–water characteristic curves (SWCCs) and pore-size distribution curves (PSDs) of compacted loess specimens with different molding water contents or compaction energies were determined. Moreover, the PSDs of compacted loess specimens dried to different suctions were measured and the fractal dimensions of these specimens were examined to explore the microstructural evolution of compacted loess during drying. The results show that molding water content mainly affects the densities of macropores and mesopores, and compaction energy only affects the density of macropores. As the molding water content range of 16% to 20%, the AEV decreases with the increase of molding water content. The specimen with a lower molding water content has a larger slope of SWCC (or desorption rate). Compaction energy influences the water retention capacity of compacted loess in the low suction range (< 30 kPa). In response to suction increase, the PSD of compacted loess changes a little, while the fractal dimension increases with suction and there is a good linear relationship between them, indicating that the roughness of the pore surfaces is increasing during drying. This study provides new insight into the relationship between water retention capacity and pore structure of compacted loess and the microstructural evolution of compacted loess during drying, which is meaningful to the prevention of loess geological hazards.

Intrarenal Pressure with Vacuum-Assisted Ureteral Access Sheaths Using an In Situ Cadaveric Porcine Model.

Introduction: Vacuum-assisted ureteral access sheaths (V-UASs) are a new tool designed to evacuate dust or small fragments during retrograde intrarenal surgery (RIRS). There are reports of increased stone-free rates, decreased infections, and decreased operative time with V-UAS usage. The optimal technique and setting for V-UAS has yet to be described. Herein, we investigate real-time intrarenal pressure (IRP) throughout a range of settings using V-UAS in a porcine RIRS model. Materials and Methods: Ureteroscopy was performed in three female porcine cadaver kidneys through a ClearPetra V-UAS. IRP was recorded through a percutaneous catheter at different inflow pressures, sheath sizes, sheath distance from the ureteropelvic junction, and suction settings. Magnitude of change in delta IRP (dIRP) was compared at various settings. Results: There was no statistical difference in IRP when comparing no suction with vent inactivated. As expected, IRP decreased with larger sheath size and lower irrigation pressures. Average IRP dropped ∼18 mm Hg with suction activation (42.30 mm Hg, vent inactivated; 24.45 mm Hg IRP, suction activated; p < 0.0001). Irrigation pressure and sheath size did not make a difference in the dIRP. dIRP was significantly greater at lower suction settings compared with max suction (25.44 dIRP at 200 mm Hg suction, 10.26 mm Hg dIRP at max suction, p = 0.04). In a subset of observations, IRP paradoxically increased to higher than IRP with no suction at all after >5 seconds of activated suction. Conclusion: Use of V-UAS during RIRS can lower mean IRP; however, this effect could reverse with extended suctioning especially under conditions of high vacuum (>200 mm Hg) owing to outflow tract collapse. Our results suggest urologists should use lower suction settings and short, <5-second bursts to maximize therapeutic benefit, and minimize potential shortcomings of V-UAS during RIRS.

Breast Fat Grafting: 10-Year Learned Clinical Experience

Our being strives for staying youthful and being beautiful. Beauty for woman encompasses the entire body from the face, down to the breasts, the torso, buttocks, and extremities. Breast enhancement using implants is consistently ranked as one of the most common aesthetic surgical procedure undertaken by woman. However, as alloplastic implants suffer numerous potential complications and revision surgery, some practitioners and patients seek alternative treatment. Autologous fat grafting has gained popularity due to its safety and scientific advances yielding increased adipocyte survival. The low complication rate and valuable cosmetic outcomes will continue to have patients request natural breast augmentation. The authors’ more than 12 years of clinical experience with autologous fat transfer to the breast is presented. Advances in fat processing, enrichment, and administration are highlighted. The addition of stem cells, stromal vascular fraction, and platelet-rich plasma (PRP) is elucidated during the clinical experience. Laboratory evaluation of fat survival comparing ultrasound- and suction-assisted fat harvesting is presented. A comparison of 2 distinct fat processing methods is done using both clinical evaluation by the patients and surgeon, and the use of diagnostic ultrasound to assess fat thickness before and after surgical placement. The filtration device (Puregraft, Solana Beach, California) was compared with the Lipokit or filtration, centrifugation device (Medi-Khan USA, Inc., Los Angeles, California). Breast fat grafting was used for sole breast augmentation, after silicone breast implant surgery, in conjunction with mammopexy surgery, and reconstruction after breast cancer surgery or explantation. The authors’ observation with breast fat grafting volumetric outcomes has seen an increase from about 30% to almost 80%. This increased volume is related to the placement of a purer fat graft with less wetting solution fluid with less blood and oil. Minimizing ultrasound energy during the harvesting, lower suction levels, short fat storage times of 1 to 2 hours prior to administration, purification of fat without washing away growth factors, and the enrichment of fat with fat-derived autologous stem cells and blood-derived PRP have been observed techniques to optimize fat survival. Breast fat grafting using much of the current knowledge of harvesting, processing, enrichment, and administration has yielded superior adipocyte survival. This increased survival has provided more consistent breast enhancement results.

Effects of innovative long-term soil and crop management on topsoil properties of a Mediterranean soil based on detailed water retention curves

Abstract. The effectiveness of conservation agriculture (CA) and other soil management strategies implying a reduction of tillage has been shown to be site-dependent (crop, clime and soil), and thus any new soil and crop management should be rigorously evaluated before its implementation. Moreover, farmers are normally reluctant to abandon conventional practices if this means putting their production at risk. This study evaluates an innovative soil and crop management (including no-tillage, cover crops and organic amendments) as an alternative to conventional management for rainfed cereal cropping in a calcareous soil in a semi-arid Mediterranean climatic zone of Navarra (Spain), based on the analysis of soil water retention curves (SWRCs) and soil structure. The study was carried out in a small agricultural area in the municipality of Garínoain (Navarre, Spain) devoted to rainfed cereal cropping. No other agricultural area in the whole region of Navarre exists where soil and crop management as proposed herein is practiced. Climate is temperate Mediterranean, and the dominant soil is Fluventic Haploxerept. Within the study area there is a subarea devoted to the proposed soil and crop management (OPM treatment), while there is another subarea where the soil and crop management is conventional in the zone (CM treatment). OPM includes no-tillage (18 years continuous) after conventional tillage, crop rotation, use of cover crops and occasional application of organic amendments. CM involves continuous conventional tillage (chisel plow), mineral fertilization, no cover crops and a lower diversity of crops in the rotation. Undisturbed soil samples from the topsoil and disturbed samples from the tilled layer were collected for both systems. The undisturbed samples were used to obtain the detailed SWRCs in the low suction range using a HYPROP©device. From the SWRCs, different approaches found in the literature to evaluate soil physical quality were calculated. The pore-size distribution was also estimated from the SWRCs. Disturbed samples were used in the laboratory to assess soil structure by means of an aggregate-size fractionation and to perform complementary analysis from which other indicators related to soil functioning and agricultural sustainability were obtained. The approaches evaluated did not show clear differences between treatments. However, the differences in soil quality between the two forms of management were better observed in the pore size distributions and by the analysis of the size distribution and stability of soil aggregates. There was an overabundance of macropores under CM, while the amount of mesopores (available water) and micropores were similar in both treatments. Likewise, more stable macroaggregates were observed in OPM than in CM, as well as more organic C storage, greater microbial activity, and biomass. The proposed management system is providing good results regarding soil physical quality and contributing also to the enhancement of biodiversity, as well as to the improvement in water-use efficiency. Finally, our findings suggest that the adoption of the proposed practice would not result in a loss in yields compared to conventional management.

Light thinning can improve soil water availability and water holding capacity of plantations in alpine mountains.

The establishment of large-scale forest plantations in the arid and semi-arid area of the Qilian Mountains in China has effectively protected water and soil resources and enhanced carbon sequestration capacity of forest ecosystems. However, the effects of different management practices in these plantations on soil water holding capacity (SWHC) and soil water availability (SWA) are uncertain in this fragile ecosystem. Here, we investigated the effects of no thinning (NT), light thinning (LT, 20% thinning intensity), and heavy thinning (HT, 40% thinning intensity) on SWHC and SWA in different soil depths of a forest plantation, and compared them to those in a natural Picea crassifolia forest (NF). Our results revealed that at low soil water suction stage, SWHC in the plantations (LT, HT, and NT) was greater in the topsoil layer (0-40 cm) than that in the NF site, while SWHC in the subsoil layer (40-80 cm) in NF was significantly greater than that in the thinning stands. At medium and high-water suction stage, SWHC in LT and NF stands was greater than that in HT and NT. Soil water characteristic curves fitted by VG model showed that the relative change in soil water content in LT topsoil layer was the smallest and SWHC was greatest. Changes in soil physicochemical properties included higher bulk density and lower total porosity, which reduced the number of macropores in the soil and affected SWHC. The bulk density, total porosity, silt content, and field capacity were the main factors jointly affecting SWA. High planting density was the main reason for the low SWA and SWHC in NT, but this can be alleviated by stand thinning. Overall, 20% thinning intensity (light intensity thinning) may be an effective forest management practice to optimize SWHC and SWA in P. crassifolia plantations to alleviate soil water deficits.

In vivo measurement of breast tissues stiffness using a light aspiration device

BackgroundThis paper addresses the question of the in vivo measurement of breast tissue stiffness, which has been poorly adressed until now, except for elastography imaging which has shown promising results but which is still difficult for clinicians to use on a day-to-day basis. Estimating subject-specific tissue stiffness is indeed a critical area of research due to the development of a large number of Finite Element (FE) breast models for various medical applications. MethodsThis paper proposes to use an original aspiration device, put into contact with breast surface, and to estimate tissue stiffness using an inverse analysis of the aspiration experiment. The method assumes that breast tissue is composed of a bilayered structure made of fatty and fribroglandular tissues (lower layer) superimposed with the skin (upper layer). Young moduli of both layers are therefore estimated based on repeating low intensity suction tests (<40 mbar) of breast tissues using cups of 7 different diameters. FindingsSeven volunteers were involved in this pilot study with average Young moduli of 56.3 kPa ± 16.4 and 3.04 kPa ± 1.17 respectively for the skin and the fatty and fibroglandular tissue. The measurements were carried out in a reasonable time scale (<60 min in total) without any discomfort perceived by the participants. These encouraging results should be confirmed in a clinical study that will include a much larger number of volunteers and patients.

Thermodynamic analysis and LCCP evaluation of kangaroo heat pump cycle for electric vehicles

The performance of heat pumps in electric vehicles drops significantly at low ambient temperatures due to low suction density and high-pressure ratios. To resolve this issue, we proposed the kangaroo heat pump cycle (KC). It is an enhanced flash tank-based vapor injection heat pump cycle (FT-VIC) that adds a sub-cycle before the refrigerant enters the flash tank, which increases the injection mass flow rate and leads to a higher heating capacity. Thermodynamic cycle models were developed for the basic heat pump cycle, FT-VIC, and KC. Furthermore, their heating performances, the annual energy consumption, and life cycle climate performance (LCCP) were evaluated and compared while using R-1234yf as the refrigerant. Results show that as compared to the FT-VIC, the KC increases the heating capacity by 25.7% and 20.1% and reduces the coefficient of performance by 25.8% and 18.9% when the ambient temperature is −5 °C and −15 °C, respectively. Due to the additional weight of the sub-cycle, the LCCP of KC is on average 4.6% higher than that of FT-VIC. In conclusion, the KC can provide more heating capacity in extremely cold conditions with additional energy consumption but is still more efficient than relying on the low-efficient PTC heater to meet the target heating capacity.

Benchtop Evaluation of Miniature Percutaneous Nephrolithotomy Lithotrites

Introduction: Percutaneous nephrolithotomy (PCNL) is the preferred treatment for kidney stones >2 cm. While PCNL has traditionally been performed using 24F to 30F access sheaths, there is a trend toward smaller sheaths and scopes to perform mini-PCNL (mPCNL). We performed benchtop assessment of multiple mPCNL lithotrites. Methods: One 1 cm3, hard Begostone phantom was placed in a cylinder with four 5.5 mm cylindrical openings to simulate the size of a 16.5F mPCNL sheath. Lithotripsy was performed with the 1.5 and 1.9 mm Trilogy, 1.83 mm ShockPulse, or a 200 μm Holmium:YAG (Ho:YAG) laser. Suction was used for the mechanical lithotrites. The Trilogy probes were set at 50% impact, 6 Hz, 80% ultrasound and 10% suction. The ShockPulse was used at high-power setting with low suction. The 1.9 mm Trilogy probe was used with a 15F mini-nephroscope. The 1.83 mm ShockPulse, 1.5 mm Trilogy and laser fiber were used with a 12F mini-nephroscope. The 120 W holmium laser was set at 0.5 J/70 Hz Moses-Distance. Ten independent runs were performed with modality. Time to complete stone clearance was recorded and mass stone clearance rates were calculated. Results: The Trilogy 1.9 mm showed superior stone clearance rate (11.69 ± 3.68 mg/s) vs the ShockPulse (SP) 1.83 mm (6.29 ± 1.37 mg/s, p = 0.003), the laser fiber (4.73 ± 0.61 mg/s, p < 0.0005), and the Trilogy 1.5 mm (6.84 ± 1.21 mg/s). The 200 μm laser fiber was inferior to all mechanical lithotrites. There was no difference between the 1.5 mm Trilogy and the 1.83 mm ShockPulse (p = 0.772). This translates to 3.9, 4.8, and 8.1 minutes less treatment time vs the 1.5 mm Trilogy, SP, and laser, respectively, for a spherical 1.5 cm diameter calcium oxalate monohydrate stone. Conclusion: Among these four commonly used mPCNL lithotripters, the Trilogy 1.9 mm demonstrated superior stone clearance rates in this benchtop model vs the Ho:YAG laser, 1.83 mm SP, and Trilogy 1.5 mm. Future clinical testing is warranted to evaluate the optimal lithotrite for mPCNL.

About the “Heat Shock” Phenomenon

At present, depletion and diminished performance of oil formations take place. Operation of low production wells is carried out using ESP units at the rate of max. 35 m3/per day under low suction pressure of centrifugal pumps. The drop of the centrifugal pump suction pressure below the saturation pressure leads to liberation of free gas in the pumped mixture. Operation of a centrifugal pump during pumping of gas-cut mixtures results in reduction of the ESP unit efficiency. The loss of the pump efficiency leads to the fact that the substantial part of energy is consumed on heating and temperature rise of the centrifugal pump. Operation of a centrifugal pump at elevated temperatures results in frequent faults of the ESP units and in salt deposition. In some cases, faults of the ESP units may occur out of the blue due to the uncontrolled heat release and temperature rise. Let us call a sudden uncontrolled heating of a centrifugal pump a “heat shock”. The pump failure as a result of a heat shock is normally classified as the “wrongdoing of the oil producing organization personnel”. This article addresses the possibility of detection and elimination of the “heat shock” moment - a sudden ESP failure. Solution of this problem will be useful for design engineering of the pump automatic control.