Successive Shock Waves Research Articles

Direct Numerical Simulation of Supersonic Gas Flow Through a Circular Cylindrical Channel

The results of the theoretical solution of the problem of braking a supersonic flow in a round pipe based on direct numerical simulation by integrating the Navier – Stokes equations without the use of additional models and empirical constants are shown. Shaded maps of density distribution depending on flow parameters are presented. The flow consists of successive rhombus-shaped shock waves distributed along the entire length of the channel. It is determined that the size of x-shaped structures depends on the flow parameters. At a lower Mach number, the rhombuses have a smaller size and, accordingly, their number increases along the length of the channel. The Reynolds number also affects the size of structures, however, it is less pronounced. With a lower Reynolds number, x-shaped structures have a smaller size. It is shown that over time the flow tends to a stationary state.

Characteristics of “Dust” Fluxes from the Surface of Copper and Lead Liners Exposed to One or Two Successive Shock Waves

Comparative experimental studies of the shock-induced particle ejection (“dusting”) from the free rough (Rz20) surface of copper and lead liners exposed to one or two successive shock waves separated in time by 0.2 μs have been carried out for the first time. This situation usually occurs in cumulative systems for the compression of the plasma by cylindrical or spherical liners shock or quasi-isentropically accelerated by explosion products. Using pulsed X-ray diffraction, laser optical recording, piezoelectric pressure sensors, and heterodyne interferometry, a qualitative picture has been studied and the quantitative characteristics of particle ejection from the free surface such as the velocities of the free surface and the particle flux front and the density (mass) distribution of particle flux in the direction of its motion, which are necessary for more accurate determination of features and the development of more appropriate models of the effect, have been evaluated.

Experimental study on a light–heavy interface evolution induced by two successive shock waves

Richtmyer–Meshkov instability induced by two successive shock waves is experimentally studied in a specific shock tube. To create two successive shock waves synchronously, a driver section is added between the driver and driven sections of the standard shock tube, and an electronically controlled membrane rupture equipment is adopted. The shock-tube flow after the membranes rupture is well described by combining the shock relations, isentropic wave relations with compatibility relations across the contact surface (region). The new shock tube is capable of generating two successive shock waves with controllable strengths and time interval, and provides a relatively ‘clean’ wave system. Then the developments of single-mode light–heavy interfaces with different initial conditions induced by two successive shock waves are investigated. The initial amplitudes are all small enough such that the first-shocked interface is within the linear growth regime at the arrival of the second shock. The results show that if the pre-second-shock perturbation amplitude is small, the linear, nonlinear and modal evolutions of the double-shocked interface can be reasonably predicted by the existing models proposed for predicting the perturbation growth induced by a single shock. For the double-shocked interface, the second shock provides an additional perturbation velocity field to the original one introduced by the first shock impact. The validity of the linear superposition model indicates that the linear superposition of these two perturbation velocity fields is satisfied. Therefore, a double-shocked interface evolves similarly to a single-shocked interface provided that their postshock amplitudes and linear growth rates are the same.

Finite-time singularity associated with the deflagration-to-detonation transition on the tip of an elongated flame-front in a tube

The critical condition for the deflagration to detonation transition (DDT) on the tip of elongated flames in tubes is revisited. Outstanding experiments and numerics, performed in 2010, have shown that a train of successive shock waves is produced by the self-accelerating flame-front. A pre-conditioned state is thus generated just prior to the DDT in a slice of unreacted gas adjacent to the flame front with a temperature too low for self-ignition, leaving unexplained the abrupt transition. Using a simplified one-dimensional model, the objective of the theoretical analysis of this short note is to identify the pre-conditioned state just prior to the spontaneous formation of a flow singularity on the flame front. This finite-time singularity responsible for the DDT is produced by the least further increase in propagation velocity beyond a critical value. The attention is focused on the unsteady compression waves emitted in the unreacted gas by the self-accelerating flame front. The unsteady effects were overlooked by the previous theoretical analyses.

Predictors of successful emergency shock wave lithotripsy for acute renal colic

The role of emergency shockwave lithotripsy (SWL) in persistent pain control in patients with ureteral stones is not well established. The aim of this study is to evaluate efficacy as well as the predicting variables for successful early SWL patients with symptomatic ureteral stones. Eighty-six patients with a persistent renal colic secondary to single ureteral stone (6–12 mm) were prospectively enrolled in this study. SWL was performed within 24 h of the onset of flank pain. Pain control and stone-free rate after emergency SWL session were 58.1% and 44.2%, respectively. Seven patients required post-SWL ureteroscopy and ureteral stent placement for uncontrolled pain. The overall 3-month stone-free rate after SWL monotherapy was 83.7%. On multivariate analysis, predictors for pain relief after emergency SWL were lower Hounsfield (HU) stone density, mild hydronephrosis (HN) at presentation and presentation during the first colic episode. Lower HU stone density was the single predictor of successful stone clearance after single emergency SWL session on multivariate analysis. In conclusion, early SWL is feasible and effective in management of ureteral stones presented by renal colic with low HU.

Comparative study on single-incident and dual-incident shock wave/turbulent boundary layer interactions with identical total deflection angle

Interactions between the boundary layer and two successive incident shock waves (ISWs) often occur in the supersonic mixed-compression inlets. However, the flow mechanism involved in such interactions has been studied rarely. In this study, we investigate experimentally and analytically the turbulent boundary layer separation flow induced by the single ISW and dual ISWs at the identical total deflection angles in a Mach 2.73 flow. Schlieren photography, wall pressure measurement and surface oil-flow visualisation are employed to diagnose the flow field. Experiments with the impingement points of the two ISWs intersecting on the bottom wall exhibit a separated flow with a triangle-like separation bubble, namely the first kind of dual-ISW/turbulent boundary layer interaction (ISWTBLI). Comparative studies show that various flow features of this kind of dual-ISWTBLI, including the extent of the separation region, pressure distribution and surface-flow topological structures, are nearly identical to those of the single-ISWTBLI with an identical total deflection angle. As the distance between the two ISWs increases, the shape of the separation region in the dual-ISWTBLI changes from triangle-like to quadrilateral-like, and the height of the separation region decreases accordingly, forming the second kind of dual-ISWTBLI. Furthermore, an inviscid model is developed for the dual-ISWTBLI to describe the complex shock wave system and elucidate the cause of a quadrilateral-like separation bubble in the second kind of dual-ISWTBLI. Moreover, based on a previous work by Souverein et al. (J. Fluid Mech., vol. 714, 2013, pp. 505–535) on the single-ISWTBLI, a modified scaling method is established for the first kind of dual-ISWTBLI.

Structural, optical and magnetic properties of silver oxide (AgO) nanoparticles at shocked conditions

Silver oxide nanoparticles (AgO NPs) were synthesized by implementing chemical reduction process and two different samples of AgO NPs were loaded with 100 as well as 200 pulses of successive shock waves of Mach number 2.2 so as to investigate the aftermath effect. Various characteristic analytical techniques were carried out for the samples utilizing Powder X-ray diffractometer (PXRD), Ultra-Violet diffuse reflectance spectroscope (UV-DRS), Field emission scanning electron microscope (FE-SEM) and Vibrating sample magnetometer (VSM) to find stabilities of crystallographic, spectroscopic, morphological and magnetic behaviors and also to analyze the changes occurring on the properties of the test material due to the impulsion of shock waves. From the obtained XRD patterns, the mean value of grain sizes of unshocked, 100 and 200 shocked AgO NPs is found to be 20, 20.6 and 26 nm, respectively. FE-SEM images reveal that the mean values of particle sizes increase as the counting of shock pulses are increased. The particles sizes are computed to be 72 nm, 112 nm, and 162 nm for the unshocked, 100 and 200 shocked AgO NPs, respectively. Whereas, the values of magnetization of AgO NPs have reduced with regard to the number of shock waves in such a way that the value of 2.183 emu/g for the unshocked AgO NPs is found to have reduced to 1.801 and 1.416 emu/g for 100 and 200 shocks, receptively. The band gap energy of the unshocked and shocked AgO NPs is observed to have the same value of 2.1 eV. From the experiential results, it is very well established that the title material’s properties such as crystalline and molecular structure, band gap energy are stable; whereas, the magnetic properties and surface morphology undergo subtle changes at shocked conditions.

The accretion disc-jet connection in blazars

The power spectral density (PSD) of the X-ray emission variability from the accretion disc-corona region of black hole X-ray binaries and active galactic nuclei has a broken power law shape with a characteristic break time-scale. If the disc and the jet are connected, the jet variability may also contain a characteristic time-scale related to that of the disc-corona. Recent observations of the blazar Mrk 421 have confirmed the broken power law shape of the PSD of its jet X-ray variability. We model the time variability of a blazar, in which emitting particles are assumed to be accelerated by successive shock waves flowing down the jet with a varying inter-shock time-scale. We investigate the possible relation between the characteristic time-scales in the disc and jet variability based on the above model, along with mathematically and physically simulated disc variability. We find that both the PSD of the jet and disc variability may have a broken power law shape but the break time-scales are not related in general except only in systems with a small range of BH mass. The break in the jet and the disc PSD are connected to the interval between large amplitude outbursts in the jet (inter-shock time-scale) and to the viscous time-scale in the disc, respectively. In frequency bands where multiple emission processes are involved or emission is from lower energy particles, the break in the PSD may not be prominent enough for detection.

Three-Dimensional Texture Analysis with Machine Learning Provides Incremental Predictive Information for Successful Shock Wave Lithotripsy in Patients with Kidney Stones

We sought to determine the predictive value of 3-dimensional texture analysis of computerized tomography images for successful shock wave lithotripsy in patients with kidney stones. Patients with preoperative and postoperative computerized tomography, previously untreated kidney stones and a stone diameter of 5 to 20 mm were included in study. A total of 224, 3-dimensional texture analysis features of each kidney stone, including attenuation measured in HU and the clinical variables body mass index, initial stone size and skin to stone distance, were analyzed using 5 commonly used machine learning models. The data set was split in a ratio of 2/3 for model derivation and 1/3 for validation. Machine learning based predictions of shock wave lithotripsy success in the validation cohort were evaluated by calculating sensitivity, specificity and the AUC. For shock wave lithotripsy success the 3 clinical variables body mass index, initial stone size and skin to stone distance showed an AUC of 0.68, 0.58 and 0.63, respectively. No predictive value was found for HU. A random forest classifier using 3, 3-dimensional texture analysis features had an AUC of 0.79. By combining these 3 features with clinical variables discriminatory accuracy improved further with an AUC of 0.85 for 3-dimensional texture analysis features and skin to stone distance, an AUC of 0.8 for 3-dimensional texture analysis features and body mass index, and an AUC of 0.81 for 3-dimensional texture analysis and stone size. This preliminary study indicates that the clinical variables body mass index, initial stone size and skin to stone distance show limited value to predict shock wave lithotripsy success while stone HU values were not predictive. Select 3-dimensional texture analysis features identified by machine learning provided incremental accuracy to predict the success of shock wave lithotripsy.

PD08-03 3D TEXTURE ANALYSIS IN ABDOMINAL CT AIDED BY MACHINE LEARNING CLASSIFIERS PREDICTS SHOCK WAVE LITHOTRIPSY SUCCESS

You have accessJournal of UrologyStone Disease: Shock Wave Lithotripsy1 Apr 2018PD08-03 3D TEXTURE ANALYSIS IN ABDOMINAL CT AIDED BY MACHINE LEARNING CLASSIFIERS PREDICTS SHOCK WAVE LITHOTRIPSY SUCCESS Manoj Mannil, Jochen von Spiczak, Thomas Hermanns, Hatem Alkhadi, and Christian Fankhauser Manoj MannilManoj Mannil More articles by this author , Jochen von SpiczakJochen von Spiczak More articles by this author , Thomas HermannsThomas Hermanns More articles by this author , Hatem AlkhadiHatem Alkhadi More articles by this author , and Christian FankhauserChristian Fankhauser More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.449AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Predictive variables for successful shock wave lithotripsy (SWL) in patients with kidney stones include stone composition, size, shape, skin-to-stone distance (SSD) and mean calculus attenuation in Hounsfield Units (HU). However, CT attenuation values are influenced by differences in CT scan protocol settings, region-of-interest (ROI) delineation, magnification and windowing. Therefore published CT attenuation thresholds vary from 593 HU to 1350 HU and correlations between CT attenuation and success of SWL ranges considerably between studies. The aim of this study was to overcome the limitation of CT attenuation thresholds by applying 3D texture analysis (TA). METHODS CT was performed on patients with nephrolithiasis. All patients underwent SWL and received an abdominal CT examination before and after treatment and successful SWL was defined as residual stone size < 2 mm. 3D TA was performed on initial CT after postprocessing for pixel spacing and image normalization. We tested five commonly used machine learning-based models: (1) J48 decision tree (2) k-nearest neighbour (kNN), (3) artificial neural network (aNN) with backpropagation (Multilayer Perceptron), (4) Random Forest, and (5) sequential minimal optimization (SMO). In order to account for overfitting, the data set was split in the recommended ratio of 2/3 for model derivation and 1/3 for validation. Using C statistics we evaluated the discriminatory capability of uni- and multivariaable models with the 3D TA as compared with the models without 3D TA. RESULTS The model derivation and the validation cohort consisted of 34 and 17 patients with a median age of 55.5 and 53.9 years, 35% and 11% females, a median BMI of 27 and 28 and a median stone size of 10.8 and 9.1mm, respectively. Stone disintegration was successful in 22/51 (43.1 %) patients. In a multivariable model taking initial stone size, skin-to-stone distance, and BMI into account the Random Forrest represented the best predictive ability with a sensitivity of 0.59, specificity of 0.87 and an AUC of 0.81. CONCLUSIONS Our in-vivo study indicates the potential of TA to predict successful shock wave lithotripsy. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e162 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Manoj Mannil More articles by this author Jochen von Spiczak More articles by this author Thomas Hermanns More articles by this author Hatem Alkhadi More articles by this author Christian Fankhauser More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Prediction of successful shock wave lithotripsy with CT: a phantom study using texture analysis.

To apply texture analysis (TA) in computed tomography (CT) of urinary stones and to correlate TA findings with the number of required shockwaves for successful shock wave lithotripsy (SWL). CT was performed on thirty-four urinary stones in an in vitro setting. Urinary stones underwent SWL and the number of required shockwaves for disintegration was recorded. TA was performed after post-processing for pixel spacing and image normalization. Feature selection and dimension reduction were performed according to inter- and intrareader reproducibility and by evaluating the predictive ability of the number of shock waves with the degree of redundancy between TA features. Three regression models were tested: (1) linear regression with elimination of colinear attributes (2), sequential minimal optimization regression (SMOreg) employing machine learning, and (3) simple linear regression model of a single TA feature with lowest squared error. Highest correlations with the absolute number of required SWL shockwaves were found for the linear regression model (r=0.55, p=0.005) using two weighted TA features: Histogram 10th Percentile, and Gray-Level Co-Occurrence Matrix (GLCM) S(3, 3) SumAverg. Using the median number of required shockwaves (n=72) as a threshold, receiver-operating characteristic analysis showed largest area-under-the-curve values for the SMOreg model (AUC=0.84, r=0.51, p<0.001) using four weighted TA features: Histogram 10th Percentile, and GLCM S(1, 1) InvDfMom, S(3, 3) SumAverg, and S(4, -4) SumVarnc. Our in vitro study illustrates the proof-of-principle of TA of urinary stone CT images for predicting the success of stone disintegration with SWL.

Ejecta Production from Second Shock: Numerical Simulations and Experiments

From detailed numerical simulations and comparison with recent experiments, we explore ejecta production at an interface that is impulsively accelerated by two successive shock waves. The perturbed material interface demarcates the boundary between a metal and vacuum resulting in the formation of ejecta driven by the Richtmyer–Meshkov instability. The numerical simulations were performed with the astrophysical FLASH code, in which the shocked metallic response is conceptually modeled using continuum hydrodynamics. The experimental data were obtained from a two-shockwave, high-explosive tool at Los Alamos National Laboratory capable of generating ejecta from a shocked Sn surface in to a vacuum. In both the simulations and the experiment, linear growth is observed following the first shock event, while the second shock strikes a finite-amplitude interface leading to nonlinear growth. The timing of the second incident shock was varied systematically in our simulations to realize a finite-amplitude re-initialization of the RM instability driving the ejecta. We take advantage of the nonlinear growth following the second shock, to evaluate a recently proposed model for sourcing of mass in ejecta formation that accounts for shape effects through an effective wavelength. In particular, we find the agreement between simulations, experiments and the mass model is improved when such shape effects associated with the interface at the instance of second shock are incorporated. The approach outlined here of combining continuum simulations with validated nonlinear models can aid in the design of future experimental campaigns.

Duct Diameter and Size of Stones Predict Successful Extracorporeal Shock Wave Lithotripsy and Endoscopic Clearance in Patients With Chronic Pancreatitis and Pancreaticolithiasis.

The need for endoscopic therapy before extracorporeal shock wave lithotripsy (SWL) to facilitate pancreatic duct stone removal is unclear. Predictive factors associated with successful fragmentation and subsequent complete duct clearance are variable. We hypothesize pancreatic duct strictures and large stones, but not pre-SWL endotherapy, correlate with successful fragmentation and complete duct clearance. A retrospective cohort study of patients with pancreaticolithiasis who underwent SWL and endoscopic retrograde cholangiopancreatography between January 2009 and June 2014 was evaluated. Thirty-seven patients were treated. Technical success (TS) of fragmentation was achieved in 22 patients (60%). Technical success was associated with fewer stones and SWL sessions and smaller stone and duct size. By multivariate logistic regression, only duct dilation was associated with TS. Endoscopic success of complete duct clearance was achieved in 29 patients (80%). Endoscopic success was more frequent with stones 12 mm or less and with successful TS. By multivariate logistic regression, stones greater than 12 mm were associated with endoscopic failure. Pre-SWL endotherapy does not affect stone fragmentation. Patients with a dilated duct (>8 mm) and pancreatic stones 12 mm or greater were associated with unsuccessful TS and endoscopic success, respectively, and may benefit from early referral for surgical decompression.

A parameterization of the Richtmyer–Meshkov instability on a premixed flame interface induced by the successive passages of shock waves

The interactions of a sinusoidal premixed flame interface with successive shock waves are studied by numerically solving the two-dimensional, reactive Navier–Stokes equations with high resolution schemes. The focus is the development of the perturbations on the flame interface due to the Richtmyer–Meshkov (RM) instability. A single irreversible chemical reaction for a C2H4+3O2+4N2 mixture is used to represent the combustion process during the interactions. Three cases of interactions, with different initial incident shock wave strengths (Ma=1.2, 1.7 and 2.2), are studied. The multiple interactions between the flame interface and the shock and its reflection waves lead to interesting new observations that have not been presented before. To parameterize the interactions, we introduce a time scale decoupling assumption, and propose to use two decoupled time scales, i.e., the decoupled chemical reaction time scale τC and the decoupled RM instability time scale τRM. Based on this assumption, τC is considered to be decoupled from τRM, so that both time scales can be defined and determined independently. Specifically, τRM is defined as the reciprocal of vorticity magnitudes that can be obtained by performing the computations of two-dimensional RM instability in a chemically frozen flow that removes the effect of chemical reactions. On the other hand, τC is defined as the ratio of reaction zone width of an un-stretched, laminar, premixed flame to propagating speed of the flame, during the one-dimensional laminar flame propagation without considering two-dimensional RM instability. Using these definitions, our calculations show that both τC and τRM decrease with the successive interactions of the shock waves with the flame interface in all three cases, and that τC is larger than τRM at early stages of interactions and then rapidly decreases to a level comparable with τRM at later stages of interactions. We compare the two-dimensional visualizations of the perturbation development on the interface in reactive flows with those in chemically frozen flows. The comparison shows that RM instability plays an important role in early evolution, but chemical reactions dominate later, and that the evolution is correlated with the variations of τC and τRM for all cases studied here. The quantitative correlations between the ratio of τC to τRM and chemical heat release rate in all three cases are calculated. The good correlations indicate the advantage of the approaches to determine τC and τRM proposed in present study. The observation that the ratio of τC to τRM is independent of the initial strength of incident shock wave suggests that the ratio reflects the nature of reactive RM instability, hence provides a new dimensionless parameter for understanding such flows.

Role of multidetector computed tomography without contrast enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi

Objective: The aim of this study was to evaluate the role of nonenhancing computed tomography as a predictive factor for successful extracorporeal shock wave lithotripsy (ESWL) for urinary calculi to avoid the cost of ineffective ESWL. Background: Urolithiasis is a universal problem. Many methods of treatment of urolithiasis are described, among which is ESWLs. The outcome of ESWL is affected by several factors. Multidetector computed tomography (MDCT) can aid the localization of calculi and may provide accurate anatomical detail, providing valuable data such as stone size and stone density as predictors for ESWL success. Materials and methods: This study included 54 patients who presented with symptomatic renal colic and hematuria at the ESWL unit. ESWL was used as the primary treatment option for all patients. All patients were investigated by MDCT before and after ESWL treatment. Successful ESWL was defined when a patient had achieved complete clearance of the stone fragments or had small residual gravels of size less than 4 mm. ESWL failure was defined as no breakage of the stone after three sessions. Results: A high rate of ESWL success after a second session of ESWL was achieved in 26 cases (48.1%), followed by a first session in 15 cases (27.8%), with an overall success rate of 90.7% in 49 cases. Also, smaller size and density of urinary stones will increase the success rate of ESWL. Conclusion: MDCT can be used to provide valuable data on urinary stones to aid treatment decisions and predict the outcome of ESWL.

Finite element modelling of radial shock wave therapy for chronic plantar fasciitis

Therapeutic use of high-amplitude pressure waves, or shock wave therapy (SWT), is emerging as a popular method for treating musculoskeletal disorders. However, the mechanism(s) through which this technique promotes healing are unclear. Finite element models of a shock wave source and the foot were constructed to gain a better understanding of the mechanical stimuli that SWT produces in the context of plantar fasciitis treatment. The model of the shock wave source was based on the geometry of an actual radial shock wave device, in which pressure waves are generated through the collision of two metallic objects: a projectile and an applicator. The foot model was based on the geometry reconstructed from magnetic resonance images of a volunteer and it comprised bones, cartilage, soft tissue, plantar fascia, and Achilles tendon. Dynamic simulations were conducted of a single and of two successive shock wave pulses administered to the foot. The collision between the projectile and the applicator resulted in a stress wave in the applicator. This wave was transmitted into the soft tissue in the form of compression–rarefaction pressure waves with an amplitude of the order of several MPa. The negative pressure at the plantar fascia reached values of over 1.5 MPa, which could be sufficient to generate cavitation in the tissue. The results also show that multiple shock wave pulses may have a cumulative effect in terms of strain energy accumulation in the foot.

Predictive value of low tube voltage and dual-energy CT for successful shock wave lithotripsy: an in vitro study.

This study investigates the capabilities of low tube voltage computed tomography (CT) and dual-energy CT (DECT) for predicting successful shock wave lithotripsy (SWL) of urinary stones in vitro. A total of 33 urinary calculi (six different chemical compositions; mean size 6±3mm) were scanned using a dual-source CT machine with single- (120kVp) and dual-energy settings (80/150, 100/150SnkVp) resulting in six different datasets. The attenuation (Hounsfield Units) of calculi was measured on single-energy CT images and the dual-energy indices (DEIs) were calculated from DECT acquisitions. Calculi underwent SWL and the number of shock waves for successful disintegration was recorded. The prediction of required shock waves regarding stone attenuation/DEI was calculated using regression analysis (adjusted for stone size and composition) and the correlation between CT attenuation/DEI and the number of shock waves was assessed for all datasets. The median number of shock waves for successful stone disintegration was 72 (interquartile range 30-361). CT attenuation/DEI of stones was a significant, independent predictor (P<0.01) for the number of required shock waves with the best prediction at 80kVp (β estimate 0.576) (P<0.05). Correlation coefficients between attenuation/DEI and the number of required shock waves ranged between ρ=0.31 and 0.68 showing the best correlation at 80kVp (P<0.001). The attenuation of urinary stones at low tube voltage CT is the best predictor for successful stone disintegration, being independent of stone composition and size. DECT shows no added value for predicting the success of SWL.

Tu1491 Duct Diameter and Size of Stones Predict Successful Extracorporeal Shock Wave Lithotripsy (ESWL) and Endoscopic Clearance in Patients With Chronic Pancreatitis and Pancreaticolithiasis

Tu1491 Duct Diameter and Size of Stones Predict Successful Extracorporeal Shock Wave Lithotripsy (ESWL) and Endoscopic Clearance in Patients With Chronic Pancreatitis and Pancreaticolithiasis

Shifting and Persistent Human Resources’ Positional/Motivational Profiles in the Context of the Latest Economic Crisis: The Cases of Germany, The Netherlands, Spain and Portugal

Abstract The latest financial and ensuing economic crisis has created successive shock waves in the eurozone countries. Their capacity to deal effectively with the impact of the crisis depends not only on reforms introduced as a response to the need for improved competitiveness but also on how the world of work would react to them. This reaction, whether it is dynamic and change-oriented or passive and backwards-looking, is assumed to be mediated by various dispositional and positional dimensions related to both motivational values, such as self-directedness and conformity and work-related realities, such as organizational and job characteristics. This paper explores the interplay between motivational and work-related dimensions for people in employment in Germany, the Netherlands, Portugal and Spain. For this purpose, the European Social Survey datasets for the 2008 and 2012 rounds are analyzed using multidimensional techniques. The aim is to reveal and discuss dominant profiles and possible shifts between the year 2008, when the crisis began, and four years later, when its impact has been strongly felt, particularly in the last two countries.

Two Successive Shock Waves Generated by Underwater Pulse Electric Discharge for Medical Applications

This paper reports on analysis of two different types successive underwater shock waves generated by a device incorporating a compact shock-wave generator with a magnetic pulsed compression circuit. To generate shock waves, underwater pulsed electric discharges in high-impedance saline water were used. The saline water made possible underwater shock waves propagation in tissue with low reflection between the solution and tissue boundary, owing to their similar acoustic impedances. A cylindrical electrode holder and a semiellipsoidal shock-wave focusing reflector/generator were used in this paper. The diameter of the compact shock-wave reflector was 20 mm. Two kinds of successive underwater shock waves, one generated by electric discharge plasma expansion and the other by bubble collapse, were observed. The shock waves were studied by time-resolve high-speed visualization and direct pressure measurement using a fiber optic probe hydrophone pressure transducer. The former method elucidated propagation of underwater shock waves and behavior and collapse of the bubble near the electrodes, while the later measured two kinds of underwater shock waves pressures at different voltage amplitudes using the cylindrical electrode holder and the shock focusing generator. This paper clearly shows the importance of the secondary shock waves, their control, and damping, for effective and safe medical application of shock waves.