WorldWideScience

Sample records for ablation electrode-induced displacement

  1. Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids: Effect of Bowel Interposition on Procedure Feasibility and a Unique Bowel Displacement Technique

    Young-Sun Kim; Hyo Keun Lim; Hyunchul Rhim

    2016-01-01

    Purpose To evaluate the effect of bowel interposition on assessing procedure feasibility, and the usefulness and limiting conditions of bowel displacement techniques in magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) ablation of uterine fibroids. Materials and Methods Institutional review board approved this study. A total of 375 screening MR exams and 206 MR-HIFU ablations for symptomatic uterine fibroids performed between August 2010 and March 2015 were retrosp...

  2. Endometrial ablation

    Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

  3. Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids: Effect of Bowel Interposition on Procedure Feasibility and a Unique Bowel Displacement Technique.

    Young-Sun Kim

    Full Text Available To evaluate the effect of bowel interposition on assessing procedure feasibility, and the usefulness and limiting conditions of bowel displacement techniques in magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU ablation of uterine fibroids.Institutional review board approved this study. A total of 375 screening MR exams and 206 MR-HIFU ablations for symptomatic uterine fibroids performed between August 2010 and March 2015 were retrospectively analyzed. The effect of bowel interposition on procedure feasibility was assessed by comparing pass rates in periods before and after adopting a unique bowel displacement technique (bladder filling, rectal filling and subsequent bladder emptying; BRB maneuver. Risk factors for BRB failure were evaluated using logistic regression analysis.Overall pass rates of pre- and post-BRB periods were 59.0% (98/166 and 71.7% (150/209, and in bowel-interposed cases they were 14.6% (7/48 and 76.4% (55/72, respectively. BRB maneuver was technically successful in 81.7% (49/60. Through-the-bladder sonication was effective in eight of eleven BRB failure cases, thus MR-HIFU could be initiated in 95.0% (57/60. A small uterus on treatment day was the only significant risk factor for BRB failure (B = 0.111, P = 0.017.The BRB maneuver greatly reduces the fraction of patients deemed ineligible for MR-HIFU ablation of uterine fibroids due to interposed bowels, although care is needed when the uterus is small.

  4. Droplet distributions from melt displacement and ejection mechanism during Al ns-laser ablation and deposition experiments: Influence of laser spot position

    Experimental observations of the angular distribution of droplets during laser ablation and deposition of Al thin films are presented and discussed. The experimental results, obtained by simply moving the laser spot position with respect to the rotation axis of the target, allow clarification of the unexpected symmetric double peaked angular droplet distribution on the films. These results provide direct evidence that a laser fluence threshold exists, beyond which droplets are generated from a melt displacement and ejection mechanism rather than from a phase explosion. The main directions of particulate ejection are related to the particular geometry of the laser generated tracks, whose profiles depend on the relative position of the incident beam with respect to the rotation axis of the target

  5. Job Displacement

    Lori G. Kletzer

    1998-01-01

    The past decade and a half has seen tremendous research growth in the area of job displacement. This paper discusses the state of knowledge on the issues and questions of job loss. The 1984-96 Displaced Worker Surveys are used to describe how the characteristics of displacement are changing to include more college educated, white collar, and nonmanufacturing workers. For many workers, the long-term earnings losses following displacement are large due to the loss of firm-specific human capital...

  6. Displacing use

    Kelly, Janet; Matthews, Ben

    2014-01-01

    This paper critically discusses the concept of use in design, suggesting that relevant relationships other than use are sometimes obscured by the usercentredness of design processes. We present a design case from the medical device domain that displaced the concept of use from the centre of a hum...

  7. Displacement Ventilation

    Bjørn, Erik; Mattsson, Magnus; Sandberg, Mats;

    Full-scale experiments were made in a displacement ventilated room with two breathing thermal manikins to study the effect of movements and breathing on the vertical contaminant distribution, and on the personal exposure of occupants. Concentrations were measured with tracer gas equipment in the...

  8. Ablative and fractional ablative lasers.

    Brightman, Lori A; Brauer, Jeremy A; Anolik, Robert; Weiss, Elliot; Karen, Julie; Chapas, Anne; Hale, Elizabeth; Bernstein, Leonard; Geronemus, Roy G

    2009-10-01

    The field of nonsurgical laser resurfacing for aesthetic enhancement continues to improve with new research and technological advances. Since its beginnings in the 1980s, the laser-resurfacing industry has produced a multitude of devices employing ablative, nonablative, and fractional ablative technologies. The three approaches largely differ in their method of thermal damage, weighing degrees of efficacy, downtime, and side effect profiles against each other. Nonablative technologies generate some interest, although only for those patient populations seeking mild improvements. Fractional technologies, however, have gained dramatic ground on fully ablative resurfacing. Fractional laser resurfacing, while exhibiting results that fall just short of the ideal outcomes of fully ablative treatments, is an increasingly attractive alternative because of its far more favorable side effect profile, reduced recovery time, and significant clinical outcome. PMID:19850197

  9. Digital displacements

    Pors, Anja Svejgaard

    2014-01-01

    digital reforms in Denmark and shows how citizen service is transformed from service to support. The frontline employee’s classical tasks such as casework are being displaced into educational and support-oriented tasks with less professional content. Thus an unintended effect of digitisation is blurred......In recent years digital reforms are being introduced in the municipal landscape of Denmark. The reforms address the interaction between citizen and local authority. The aim is, that by 2015 at least 80 per cent of all correspondence between citizens and public authority will be transmitted through...... digital interface. However, the transformation of citizen services from traditional face-to-face interaction to digital self-service gives rise to new practices; some citizens need support to be able to manage self-service through digital tools. A mixture of support and teaching, named co...

  10. Endoscopically visible steam pop during high-energy laser pulmonary vein ablation

    Gal, P.; Smit, J. J. J; Elvan, A.

    2015-01-01

    A 58-year-old woman with atrial fibrillation underwent laser balloon ablation at our centre. During 12 W ablation in the left superior pulmonary vein, a sudden steam pop was witnessed with displacement of the balloon catheter. Visualisation of the pulmonary vein antrum showed a red discolouration at the last ablation site.

  11. Ablation of lung tumours

    Gillams, Alice

    2012-01-01

    Abstract Radiofrequency, laser, microwave and cryotherapy have all been used for the ablation of lung tumours. However, radiofrequency ablation (RFA) and microwave ablation are the most widely used technologies. RFA has been successfully applied to tumour measuring from

  12. Nanoscale ablation through optically trapped microspheres

    Fardel, Romain; McLeod, Euan; Tsai, Yu-Cheng; Arnold, Craig B.

    2010-10-01

    The ability to directly create patterns with size scales below 100 nm is important for many applications where the production or repair of high resolution and density features is needed. Laser-based direct-write methods have the benefit of being able to quickly and easily modify and create structures on existing devices, but ablation can negatively impact the overall technique. In this paper we show that self-positioning of near-field objectives through the optical trap assisted nanopatterning (OTAN) method allows for ablation without harming the objective elements. Small microbeads are positioned in close proximity to a substrate where ablation is initiated. Upon ablation, these beads are temporarily displaced from the trap but rapidly return to the initial position. We analyze the range of fluence values for which this process occurs and find that there exists a critical threshold beyond which the beads are permanently ejected.

  13. Pellet ablation and ablation model development

    A broad survey of pellet ablation is given, based primarily on information presented at this meeting. The implications of various experimental observations for ablation theory are derived from qualitative arguments of the physics involved. The major elements of a more complete ablation theory are then outlined in terms of these observations. This is followed by a few suggestions on improving the connections between theory and experimental results through examination of ablation data. Although this is a rather aggressive undertaking for such a brief (and undoubtedly incomplete) assessment, some of the discussion may help us advance the understanding of pellet ablation. 17 refs

  14. Emerging Local Ablation Techniques

    Stone, Michael J.; Wood, Bradford J.

    2006-01-01

    Local ablation technologies for hepatic malignancy have developed rapidly in the past decade, with advances in several percutaneous or externally delivered treatment methods including radiofrequency ablation, microwave ablation, laser ablation, and high-intensity focused ultrasound. Research has focused on increasing the size of the ablation zone and minimizing heat-sink effects. More recent developments include improvements in treatment planning and navigation with integration of several ima...

  15. Studies of ablation pressure, ablative acceleration and ablative implosions

    Time and space resolved X-ray spectroscopy have been used to measure ablation rate and ablation pressure on plane targets irradiated by the first and second harmonics of Nd glass laser light. Streaked X-ray shadowgraphy has been applied to the study of ablatively imploded spherical shell targets uniformly irradiated by six 1.05 μm laser beams. The results give a direct measurement of shell acceleration and thus of ablation pressure and show evidence of fluid instability increasing as the shell ratio is varied from 10 to 100. A direct determination of implosion core density is also obtained. (author)

  16. Job Displacement and Crime

    Bennett, Patrick; Ouazad, Amine

    We use a detailed employer-employee data set matched with detailed crime information (timing of crime, fines, convictions, crime type) to estimate the impact of job loss on an individual's probability to commit crime. We focus on job losses due to displacement, i.e. job losses in firms losing a...... that displaced workers' propensity to commit crime is higher than non-displaced workers before the displacement event; but it is significantly higher afterwards. Displacement impacts crime over and above what is explained by earnings losses and weeks of unemployment following displacement....

  17. Job Displacement and Crime

    Bennett, Patrick; Ouazad, Amine

    theory of crime. Marital dissolution is more likely post-displacement, and we find small intra-family externalities of adult displacement on younger family members’ crime. The impact of displacement on crime is stronger in municipalities with higher capital and labor income inequalities.......This paper matches a comprehensive Danish employer-employee data set with individual crime information (timing of offenses, charges, convictions, and prison terms by crime type) to estimate the impact of job displacement on an individual’s propensity to commit crime. We focus on displaced...... individuals, i.e. high-tenure workers with strong attachment to their firm, who lose employment during a mass-layoff event. Pre-displacement data suggests no evidence of endogenous selection of workers for displacement during mass-layoffs: displaced workers’ propensity to commit crime exhibits no...

  18. Research Paradigm of Displaced Aggression

    Tanno, Syota

    2013-01-01

    A review of research paradigm of displaced aggression is presented. The author arranged the Japanese wording of displaced aggression, summarized the historical transition of research on displaced aggression, and reviewed research paradigm of displaced aggression.

  19. Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

    Milos, Frank S.; Chen, Yih K.; Gokcen, Tahir

    2012-01-01

    In previous work, an equilibrium ablation and thermal response model for Phenolic Impregnated Carbon Ablator was developed. In general, over a wide range of test conditions, model predictions compared well with arcjet data for surface recession, surface temperature, in-depth temperature at multiple thermocouples, and char depth. In this work, additional arcjet tests were conducted at stagnation conditions down to 40 W/sq cm and 1.6 kPa. The new data suggest that nonequilibrium effects become important for ablation predictions at heat flux or pressure below about 80 W/sq cm or 10 kPa, respectively. Modifications to the ablation model to account for nonequilibrium effects are investigated. Predictions of the equilibrium and nonequilibrium models are compared with the arcjet data.

  20. Lung Ablation: Whats New?

    Xiong, Lillian; Dupuy, Damian E

    2016-07-01

    Lung cancer had an estimated incidence of 221,200 in 2015, making up 13% of all cancer diagnoses. Tumor ablation is an important treatment option for nonsurgical lung cancer and pulmonary metastatic patients. Radiofrequency ablation has been used for over a decade with newer modalities, microwave ablation, cryoablation, and irreversible electroporation presenting as additional and possibly improved treatment options for patients. This minimally invasive therapy is best for small primary lesions or favorably located metastatic tumors. These technologies can offer palliation and sometimes cure of thoracic malignancies. This article discusses the current available technologies and techniques available for tumor ablation. PMID:27050331

  1. Ablative Thermal Protection System Fundamentals

    Beck, Robin A. S.

    2013-01-01

    This is the presentation for a short course on the fundamentals of ablative thermal protection systems. It covers the definition of ablation, description of ablative materials, how they work, how to analyze them and how to model them.

  2. Laser ablation principles and applications

    1994-01-01

    Laser Ablation provides a broad picture of the current understanding of laser ablation and its many applications, from the views of key contributors to the field. Discussed are in detail the electronic processes in laser ablation of semiconductors and insulators, the post-ionization of laser-desorbed biomolecules, Fourier-transform mass spectroscopy, the interaction of laser radiation with organic polymers, laser ablation and optical surface damage, laser desorption/ablation with laser detection, and laser ablation of superconducting thin films.

  3. Displacement Data Assimilation

    Rosenthal, W Steven; Mariano, Arthur J; Restrepo, Juan M

    2016-01-01

    We show that modifying a Bayesian data assimilation scheme by incorporating kinematically-consistent displacement corrections produces a scheme that is demonstrably better at estimating partially observed state vectors in a setting where feature information important. While the displacement transformation is not tied to any particular assimilation scheme, here we implement it within an ensemble Kalman Filter and demonstrate its effectiveness in tracking stochastically perturbed vortices.

  4. Internal displacement in Burma.

    Lanjouw, S; Mortimer, G; Bamforth, V

    2000-09-01

    The internal displacement of populations in Burma is not a new phenomenon. Displacement is caused by numerous factors. Not all of it is due to outright violence, but much is a consequence of misguided social and economic development initiatives. Efforts to consolidate the state by assimilating populations in government-controlled areas by military authorities on the one hand, while brokering cease-fires with non-state actors on the other, has uprooted civilian populations throughout the country. Very few areas in which internally displaced persons (IDPs) are found are not facing social turmoil within a climate of impunity. Humanitarian access to IDP populations remains extremely problematic. While relatively little information has been collected, assistance has been focused on targeting accessible groups. International concern within Burma has couched the problems of displacement within general development modalities, while international attention along its borders has sought to contain displacement. With the exception of several recent initiatives, few approaches have gone beyond assistance and engaged in the prevention or protection of the displaced. PMID:11026156

  5. Radiofrequency ablation in dermatology

    Sachdeva Silonie

    2007-01-01

    Full Text Available Radiofreqeuency ablation is a versatile dermatosurgical procedure used for surgical management of skin lesions by using various forms of alternating current at an ultra high frequency. The major modalities in radiofrequency are electrosection, electrocoagulation, electrodessication and fulguration. The use of radiofrequency ablation in dermatosurgical practice has gained importance in recent years as it can be used to treat most of the skin lesions with ease in less time with clean surgical field due to adequate hemostasis and with minimal side effects and complications. This article focuses on the major tissue effects and factors influencing radiofrequency ablation and its application for various dermatological conditions.

  6. Liver tumor ablation

    Minimal-invasive techniques for ablation of primary and secondary hepatic tumors gain increasingly clinical importance. This is especially true since surgical resection and classic chemotherapy is successful only in a limited number of patients. Local ablative methods incorporate chemo- (percutaneous alcohol instillation, transarterial chemoembolization), thermo- (radiofrequency-, laser-, microwave-, cryoablation, high intensive focused ultrasound) and radio-ablative techniques (interstitial brachytherapy, selective internal radiotherapy). Regarding their implementation and specific effects these methods are varying widely, nevertheless all of them have a high therapeutical efficacy together with a low complication rate in common - correct application presumed. The knowledge on specific indications and contraindications is crucial to implement these methods into multimodality therapy concepts. (orig.)

  7. Microwave Ablation of Hepatic Malignancy

    Lubner, Meghan G.; Brace, Christopher L.; Ziemlewicz, Tim J.; Hinshaw, J. Louis; Lee, Fred. T.

    2013-01-01

    Microwave ablation is an extremely promising heat-based thermal ablation modality that has particular applicability in treating hepatic malignancies. Microwaves can generate very high temperatures in very short time periods, potentially leading to improved treatment efficiency and larger ablation zones. As the available technology continues to improve, microwave ablation is emerging as a valuable alternative to radiofrequency ablation in the treatment of hepatic malignancies. This article rev...

  8. femtosecond laser ablation

    Margetic, Vanja

    2003-01-01

    Femtosecond laser ablation was investigated as a solid sampling method for elemental chemical analysis. In comparison to the sampling with longer laser pulses, two aspects could be improved by using ultrashort pulses: elimination of the elemental fractionation from the ablation crater, which is necessary for an accurate quantitative analysis, and better control of the material removal (especially for metals), which increases the spatial resolution of microanalysis. Basic aspects of ultrashort...

  9. The photoelectric displacement converter

    Dragoner, Valeriu V.

    2005-02-01

    In the article are examined questions of constructing photoelectric displacement converter satisfying demands that are stated above. Converter has channels of approximate and precise readings. The approximate reading may be accomplished either by the method of reading from a code mask or by the method of the consecutive calculation of optical scale gaps number. Phase interpolator of mouar strips" gaps is determined as a precise measuring. It is shown mathematical model of converter that allow evaluating errors and operating speed of conversion.

  10. HIGH TEMPERATURE DISPLACEMENT SENSOR

    Xu Longxiang; Zhang Jinyu; Schweitzer Gerhard

    2005-01-01

    A high temperature displacement sensor based on the principle of eddy-current is investigated. A new temperature compensation technique by using eddy-current effect is presented to satisfy the special requirement at high temperature up to 550℃. The experiment shows that the temperature compensation technique leads to good temperature stability for the sensors. The variation of the sensitivity as well as the temperature drift of the sensor with temperature compensation technique is only about 7.4% and 90~350 mV at 550℃ compared with that at room temperature, and that of the sensor without temperature compensation technique is about 31.2% and 2~3 V at 550℃ compared with that at room temperature. A new dynamic calibration method for the eddy-current displacement sensor is presented, which is very easy to be realized especially in high frequency and at high temperatures. The high temperature displacement sensors developed are successfully used at temperature up to 550℃ in a magnetic bearing system for more than 100 h.

  11. Transient Ablation of Teflon Hemispheres

    Arai, Norio; Karashima, Kei-ichi; Sato, Kiyoshi

    1997-01-01

    For high-speed entry of space vehicles into atmospheric environments, ablation is a practical method for alleviating severe aerodynamic heating. Several studies have been undertaken on steady or quasi-steady ablation. However, ablation is a very complicated phenomenon in which a nonequilibrium chemical process is associated with an aerodynamic process that involves changes in body shape with time. Therefore, it seems realistic to consider that ablation is an unsteady phenomenon. In the design of an ablative heat-shield system, since the ultimate purpose of the heat shield is to keep the internal temperature of the space vehicle at a safe level during entry, the transient heat conduction characteristics of the ablator may be critical in the selection of the material and its thickness. This note presents an experimental study of transient ablation of Teflon, with particular emphasis on the change in body shape, the instantaneous internal temperature distribution, and the effect of thermal expansion on ablation rate.

  12. Power Laser Ablation Symposia

    Phipps, Claude

    2007-01-01

    Laser ablation describes the interaction of intense optical fields with matter, in which atoms are selectively driven off by thermal or nonthermal mechanisms. The field of laser ablation physics is advancing so rapidly that its principal results are seen only in specialized journals and conferences. This is the first book that combines the most recent results in this rapidly advancing field with authoritative treatment of laser ablation and its applications, including the physics of high-power laser-matter interaction. Many practical applications exist, ranging from inertial confinement fusion to propulsion of aerostats for pollution monitoring to laser ignition of hypersonic engines to laser cleaning nanoscale contaminants in high-volume computer hard drive manufacture to direct observation of the electronic or dissociative states in atoms and molecules, to studying the properties of materials during 200kbar shocks developed in 200fs. Selecting topics which are representative of such a broad field is difficu...

  13. Optical-vortex laser ablation

    Hamazaki, Junichi; Morita, Ryuji; Chujo, Keisuke; Kobayashi, Yusuke; Tanda, Satoshi; Omatsu, Takashige

    2010-01-01

    Laser ablation of Ta plates using nanosecond optical vortex pulses was carried out, for the first time. It was suggested that owing to orbital angular momentum of optical vortex, clearer and smoother processed surfaces were obtained with less ablation threshold fluence, in comparison with the ablation by a nonvortex annular beam modified from a spatially Gaussian beam.

  14. Dispossession and displacement in Libya

    Rhodri C Williams

    2012-01-01

    Inability to access pre-displacement housing, land and property poses a significant obstacle to the achievement of durable solutions for most IDPs in Libya. Displacement and dispossession cannot be separated from the legacy of the Gaddafi era.

  15. Virtual Displacement in Lagrangian Dynamics

    Ray, S; Ray, Subhankar

    2004-01-01

    The confusion and ambiguity encountered by students, in understanding virtual displacement and virtual work, is addressed in this article. A definition of virtual displacement is presented that allows one to express them explicitly for both time independent and time dependent constraints. It is observed that for time independent constraints the virtual displacements are the displacements allowed by the constraints. However this is not so for a general time dependent case. For simple physical systems, it is shown that, the work done on virtual displacements by the constraint forces is zero in both the situations. For allowed displacements however, this is not always true. It is also demonstrated that when constraint forces do zero work on virtual displacement, as defined here, we have a solvable mechanical problem. We identify this special class of constraints, physically realized and solvable, as the ideal constraints. The concept of virtual displacement and the principle of zero virtual work by constraint fo...

  16. Displacement cascades in polyatomic materials

    Parkin, D.M.; Coulter, C.A.

    1982-01-01

    Using a continuous-slowing-down, random amorphous material model, we have studied displacement cascades in a number of diatomic materials. This paper reviews a number of previous results that elucidate the effects of atomic mass, recoil energy, displacement energy, capture energy and material stoichiometry on the numbers of displacements in a cascade. The displacement cascade reveals a complex structure that is dependent on the type of irradiation and the material properties. Conclusions related to damage analysis for fusion reactors are given.

  17. In Vivo Guidance and Assessment of Liver Radiofrequency Ablation with Acoustic Radiation Force Elastography

    Fahey, Brian J.; Nelson, Rendon C.; Hsu, Stephen J.; Bradway, David P.; Dumont, Douglas M.; Trahey, Gregg E.

    2008-01-01

    The initial results from clinical trials investigating the utility of Acoustic Radiation Force Impulse(ARFI) imaging for use with radiofrequency ablation (RFA) procedures in the liver are presented. To date, data have been collected from 6 RFA procedures in 5 unique patients. Large displacement contrast was observed in ARFI images of both pre-ablation malignancies (mean 7.5 dB, range 5.7 – 11.9 dB) and post-ablation thermal lesions (mean 6.2 dB, range 5.1 – 7.5 dB). In general, ARFI images pr...

  18. Spark ablation device

    Schmidt-Ott, A.; Pfeiffer, T.V.

    2013-01-01

    A spark ablation device for generating nanoparticles comprising a spark generator; the spark generator comprising first and second electrodes, wherein the spark generator further comprises at least one power source which is arranged to be operative at a first energy level for maintaining a discharge

  19. Tumor ablations in IMRI

    Roberto Blanco Sequeiros

    2002-01-01

    @@ IntroductionMagnetic resonance imaging based guidance control and monitoring of minimally invasive intervention has developed from a hypothetical concept to a practical possibility. Magnetic-resonance-guided interstitial therapy in principle is defined as a treatment technique for ablating deepseated tumors in the human body.

  20. Photogrammetric recession measurements of ablative materials in arcjets

    This paper describes an optical method for measuring the recession time histories of ablative thermal protection system (TPS) materials as they are tested in an arcjet facility. The method is non-intrusive and requires no external light source or modifications to the test article. It does require, first, a test article that exhibits texture as it ablates, and, second, high-resolution video images of the ablating surface from at least two directions. Software automatically reads the sequences of images and, by successive image cross correlation, tracks the deformation of a surface grid that conforms to the shape of the test article. Standard photogrammetric transformations are used to convert image-plane displacements of the surface grid to object-space displacements. The method yields a time history of the displacement of each node of the grid for the full time that the test article is exposed to the arcjet flow. Measurements have been made during many tests in the 60 MW arcjet at NASA Ames Research Center, including tests of TPS materials for the Orion Crew Exploration Vehicle and Mars Science Laboratory. The photogrammetric recession measurements have been in good agreement with post-test measurements of the change in thickness of the test articles

  1. Combined Therapeutic and Monitoring Ultrasonic Catheter for Cardiac Ablation Therapies.

    Carias, Mathew; Hynynen, Kullervo

    2016-01-01

    This study evaluated the feasibility of a combined therapeutic and diagnostic ultrasonic catheter for cardiac ablation therapies. Ultrasound can be used to determine when diseased cardiac tissues have become fully coagulated through a method known as local harmonic motion imaging (LHMI). LHMI is an imaging modality for treatment monitoring that uses acoustic radiation force, displacement tracking and the different mechanical properties of viable and ablated tissues. In this study, we developed catheters that are capable of LHMI measurements. Experiments were conducted in phantoms, ex vivo cardiac samples and the in vivo beating hearts of healthy porcine subjects. In vivo experiments revealed that four of four epicardial sonications revealed a decrease in measured displacements from LHMI experiments and that when lower power was used, no lesions formed and there was no corresponding decrease in measured displacement amplitudes. In addition, two of three endocardial lesions were confirmed and corresponded to a decrease in the measured displacement amplitude. PMID:26431798

  2. Robust Tracking of Small Displacements With a Bayesian Estimator.

    Dumont, Douglas M; Byram, Brett C

    2016-01-01

    Radiation-force-based elasticity imaging describes a group of techniques that use acoustic radiation force (ARF) to displace tissue to obtain qualitative or quantitative measurements of tissue properties. Because ARF-induced displacements are on the order of micrometers, tracking these displacements in vivo can be challenging. Previously, it has been shown that Bayesian-based estimation can overcome some of the limitations of a traditional displacement estimator such as normalized cross-correlation (NCC). In this work, we describe a Bayesian framework that combines a generalized Gaussian-Markov random field (GGMRF) prior with an automated method for selecting the prior's width. We then evaluate its performance in the context of tracking the micrometer-order displacements encountered in an ARF-based method such as ARF impulse (ARFI) imaging. The results show that bias, variance, and mean-square error (MSE) performance vary with prior shape and width, and that an almost one order-of-magnitude reduction in MSE can be achieved by the estimator at the automatically selected prior width. Lesion simulations show that the proposed estimator has a higher contrast-to-noise ratio but lower contrast than NCC, median-filtered NCC, and the previous Bayesian estimator, with a non-Gaussian prior shape having better lesion-edge resolution than a Gaussian prior. In vivo results from a cardiac, radio-frequency ablation ARFI imaging dataset show quantitative improvements in lesion contrast-to-noise ratio over NCC as well as the previous Bayesian estimator. PMID:26529761

  3. Strategies for displacing oil

    Rao, Vikram; Gupta, Raghubir

    2015-03-01

    Oil currently holds a monopoly on transportation fuels. Until recently biofuels were seen as the means to break this stranglehold. They will still have a part to play, but the lead role has been handed to natural gas, almost solely due to the increased availability of shale gas. The spread between oil and gas prices, unprecedented in its scale and duration, will cause a secular shift away from oil as a raw material. In the transport fuel sector, natural gas will gain traction first in the displacement of diesel fuel. Substantial innovation is occurring in the methods of producing liquid fuel from shale gas at the well site, in particular in the development of small scale distributed processes. In some cases, the financing of such small-scale plants may require new business models.

  4. Displacing the patient

    Pors, Anja Svejgaard

    2014-01-01

    target groups for which information can be standardized. In the latter approach (market orientation), the patient is also a resource for organizational development. Overall, the strategy presents an information-pursuing patient figure that makes it possible to streamline the organization's care...... in Copenhagen, Denmark. Based on situational analysis of internal documents, the paper gives an empirical account of the work of strategic documents and explores how the documents organize patient communication through displacements of the patient. This paper shows that the hospital’s patient...... communication is not only about disease treatment, but also about ‘information treatment’ for the purpose of increasing patient satisfaction at the hospital. The goal of patient satisfaction addresses both a care-oriented approach to the patient and also deploys market perceptions of patients as homogeneous...

  5. Displacing the Patient

    Pors, Anja Svejgaard

    as an affective care recipient, as a citizen with rights and as an individual need-oriented user on the one hand. On the other hand, the goal of patient satisfaction also deploys market perceptions of patients as homogeneous target groups to which information can be standardised. In the latter......The analysis is based on an empirical study of a hospital’s communication strategy entitled: 'The Perspective of the Patient'. The paper asks how the strategy organizes communication work as situated displacements of the patient. Based on methodological elements from situational analysis (Clarke...... 2005) the analysis examines how the hospital’s patient communication is not just about disease treatment, but rather about information treatment of the patient in order to attain a high level of patient satisfaction. The goal of patient satisfaction addresses care-oriented understandings of the patient...

  6. Displacing the patient

    Pors, Anja Svejgaard

    2012-01-01

    a care-oriented approach to the patient and also deploys market perceptions of patients as homogeneous target groups to which information can be standardized. In the latter approach (market orientation), the patient is also a resource for organizational development. Overall, the strategy presents an......This analysis is based on an empirical study of a Danish hospital‟s communication programme entitled: 'The Perspective of the Patient'. The paper explores how strategic documents of the programme organize the communication work through situated displacements of the patient. Based on methodological...... elements from situational analysis (Clarke 2005) the analysis examines how the hospital‟s patient communication is not only about disease treatment, but rather about information treatment of the patient in order to attain a high level of patient satisfaction. The goal of patient satisfaction addresses both...

  7. Displacement Parameter Inversion for a Novel Electromagnetic Underground Displacement Sensor

    Nanying Shentu; Qing Li; Xiong Li; Renyuan Tong; Nankai Shentu; Guoqing Jiang; Guohua Qiu

    2014-01-01

    Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor) by combining basic el...

  8. Displacement Parameter Inversion for a Novel Electromagnetic Underground Displacement Sensor

    Nanying Shentu

    2014-05-01

    Full Text Available Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor by combining basic electromagnetic induction principles with modern sensing techniques and established a mutual voltage measurement theoretical model called the Equation-based Equivalent Loop Approach (EELA. Based on that work, this paper presents an underground displacement inversion approach named “EELA forward modeling-approximate inversion method”. Combining the EELA forward simulation approach with the approximate optimization inversion theory, it can deduce the underground horizontal displacement through parameter inversion of the H-type sensor. Comprehensive and comparative studies have been conducted between the experimentally measured and theoretically inversed values of horizontal displacement under counterpart conditions. The results show when the measured horizontal displacements are in the 0–100 mm range, the horizontal displacement inversion discrepancy is generally tested to be less than 3 mm under varied tilt angles and initial axial distances conditions, which indicates that our proposed parameter inversion method can predict underground horizontal displacement measurements effectively and robustly for the H-type sensor and the technique is applicable for practical geo-engineering applications.

  9. Displacement parameter inversion for a novel electromagnetic underground displacement sensor.

    Shentu, Nanying; Li, Qing; Li, Xiong; Tong, Renyuan; Shentu, Nankai; Jiang, Guoqing; Qiu, Guohua

    2014-01-01

    Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor) by combining basic electromagnetic induction principles with modern sensing techniques and established a mutual voltage measurement theoretical model called the Equation-based Equivalent Loop Approach (EELA). Based on that work, this paper presents an underground displacement inversion approach named "EELA forward modeling-approximate inversion method". Combining the EELA forward simulation approach with the approximate optimization inversion theory, it can deduce the underground horizontal displacement through parameter inversion of the H-type sensor. Comprehensive and comparative studies have been conducted between the experimentally measured and theoretically inversed values of horizontal displacement under counterpart conditions. The results show when the measured horizontal displacements are in the 0-100 mm range, the horizontal displacement inversion discrepancy is generally tested to be less than 3 mm under varied tilt angles and initial axial distances conditions, which indicates that our proposed parameter inversion method can predict underground horizontal displacement measurements effectively and robustly for the H-type sensor and the technique is applicable for practical geo-engineering applications. PMID:24858960

  10. Measuring vulnerability to disaster displacement

    Brink, Susan A.; Khazai, Bijan; Power, Christopher; Wenzel, Friedemann

    2015-04-01

    Large scale disasters can cause devastating impacts in terms of population displacement. Between 2008 and 2013, on average 27 million people were displaced annually by disasters (Yonetani 2014). After large events such as hurricane Katrina or the Port-au-Prince earthquake, images of inadequate public shelter and concerns about large scale and often inequitable migration have been broadcast around the world. Population displacement can often be one of the most devastating and visible impacts of a natural disaster. Despite the importance of population displacement in disaster events, measures to understand the socio-economic vulnerability of a community often use broad metrics to estimate the total socio-economic risk of an event rather than focusing on the specific impacts that a community faces in a disaster. Population displacement is complex and multi-causal with the physical impact of a disaster interacting with vulnerability arising from the response, environmental issues (e.g., weather), cultural concerns (e.g., expectations of adequate shelter), and many individual factors (e.g., mobility, risk perception). In addition to the complexity of the causes, population displacement is difficult to measure because of the wide variety of different terms and definitions and its multi-dimensional nature. When we speak of severe population displacement, we may refer to a large number of displaced people, an extended length of displacement or associated difficulties such as poor shelter quality, risk of violence and crime in shelter communities, discrimination in aid, a lack of access to employment or other difficulties that can be associated with large scale population displacement. We have completed a thorough review of the literature on disaster population displacement. Research has been conducted on historic events to understand the types of negative impacts associated with population displacement and also the vulnerability of different groups to these impacts. We

  11. Meteoroid ablation models

    Popova, Olga

    2004-12-01

    The fate of entering meteoroids in atmosphere is determined by their size, velocity and substance properties. Material from ablation of small-sized meteors (roughly R≤0.01-1 cm) is mostly deposited between 120 and 80 km altitudes. Larger bodies (up to meter sizes) penetrate deeper into the atmosphere (down to 20 km altitude). Meteoroids of cometary origin typically have higher termination altitude due to substance properties and higher entry velocity. Fast meteoroids ( V>30-40 km/s) may lose a part of their material at higher altitudes due to sputtering. Local flow regime realized around the falling body determines the heat transfer and mass loss processes. Classic approach to meteor interaction with atmosphere allows describing two limiting cases: - large meteoroid at relatively low altitude, where shock wave is formed (hydrodynamical models); - small meteoroid/or high altitudes - free molecule regime of interaction, which assumes no collisions between evaporated meteoroid particles. These evaporated particles form initial train, which then spreads into an ambient air due to diffusion. Ablation models should make it possible to describe physical conditions that occur around meteor body. Several self-consistent hydrodynamical models are developed, but similar models for transition and free molecule regimes are still under study. This paper reviews existing ablation models and discusses model boundaries.

  12. Point Coupled Displacement Sensor Project

    National Aeronautics and Space Administration — Real-time displacement measurement techniques are needed to acquire aerodynamic and structural system characteristics in flight. This proposal describes the...

  13. Bone and Soft Tissue Ablation

    Foster, Ryan C.B.; Joseph M Stavas

    2014-01-01

    Bone and soft tissue tumor ablation has reached widespread acceptance in the locoregional treatment of various benign and malignant musculoskeletal (MSK) lesions. Many principles of ablation learned elsewhere in the body are easily adapted to the MSK system, particularly the various technical aspects of probe/antenna design, tumoricidal effects, selection of image guidance, and methods to reduce complications. Despite the common use of thermal and chemical ablation procedures in bone and soft...

  14. Displacement and resonance behaviors of a piezoelectric diaphragm driven by a double-sided spiral electrode

    Shen, Zhiyuan

    2012-04-03

    This paper presents the design of a lead zirconate titanate (PZT) diaphragm actuated by double-sided patterned electrodes. Au/Cr electrodes were deposited on bulk PZT wafers by sputtering while patterned by a lift-off process. SU-8 thick film was used to form the structural layer. Double-spiral electrode induced in-plane poling and piezoelectric elongation are converted to an out-of-plane displacement due to the confined boundary condition. The influence of different drive configurations and electrode parameters on deflection has been calculated by finite element methods (FEM) using a uniform field model. Impedance and quasi-static displacement spectra of the diaphragm were measured after poling. Adouble-sided patterned electrode diaphragm can be actuated by more drive configurations than a single-sided one. Compared with a single-sided electrode drive, a double-sided out-of-phase drive configuration increases the coupling coefficient of the fundamental resonance from 7.6% to 11.8%. The displacement response of the diaphragm increases from 2.6 to 8.6nmV 1. Configurations including the electric field component perpendicular to the poling direction can stimulate shear modes of the diaphragm. © 2012 IOP Publishing Ltd.

  15. Endoscopic ultrasound guided radiofrequency ablation in pancreas

    Seicean, Andrada; Tefas, Cristian; Ungureanu, Bogdan;

    2014-01-01

    Radiofrequency ablation of the pancreas represents a more effective tumor-destruction method compared to other ablation techniques. The endoscopic ultrasound guided radiofrequency ablation is indicated for locally advanced, non-metastatic pancreatic adenocarcinoma, without the need of general...

  16. Displacement, Substitution, Sublimation: A Bibliography.

    Pedrini, D. T.; Pedrini, Bonnie C.

    Sigmund Freund worked with the mechanisms of displacement, substitution, and sublimation. These mechanisms have many similarities and have been studied diagnostically and therapeutically. Displacement and substitution seem to fit in well with phobias, hysterias, somatiyations, prejudices, and scapegoating. Phobias, prejudices, and scapegoating…

  17. The management of climate displacement

    Scott Leckie

    2012-12-01

    Full Text Available Many of those who have fought against displacement now find themselves being advocates for resettlement and relocation. Knowing that displacements will occur as a result of climate change,the humanitarian community will need to work pre-emptively with communities identified as likely to be threatened on the land-based solutions that may be available to them.

  18. A displacement-doubling prism

    A novel prism has been devised which can be used in place of the ‘flag’ in an optical shadow-sensing type of displacement sensor, for example. In this way, theoretically the displacement sensitivity of the sensor can be doubled. Such a prism has been manufactured, and its displacement-doubling property has been verified. - Highlights: • A new type of glass prism doubles linear displacement of optical beams. • Optical operation has been verified. • Light beams enter and exit at normal incidence to prism's windows. • Optical path length through prism remains constant, as prism is moved. • Designed to double the displacement sensitivity of knife-edge shadow sensors

  19. LASER ABLATION STUDIES OF CONCRETE

    Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-s...

  20. Is Fibular Fracture Displacement Consistent with Tibiotalar Displacement?

    van den Bekerom, Michel P. J.; van Dijk, C. Niek

    2009-01-01

    We believed open reduction with internal fixation is required for supination-external rotation ankle fractures located at the level of the distal tibiofibular syndesmosis (Lauge-Hanssen SER II and Weber B) with 2 mm or more fibular fracture displacement. The rationale for surgery for these ankle fractures is based on the notion of elevated intraarticular contact pressures with lateral displacement. To diagnose these injuries, we presumed that in patients with a fibular fracture with at least ...

  1. Internal displacement in eastern Burma

    Heather Rae

    2007-07-01

    Full Text Available The history of post-independent Burma is characterisedby numerous conflicts in this extraordinarily heterogeneous country. Since military rule began in 196 2 Burmahas witnessed gross human rights abuses andmassive displacement.

  2. A novel linear displacement sensor

    Yang, Ji-sen; Zhang, Jing; Chen, Xi-hou; Zhang, Tian-heng

    2011-12-01

    With development of time grating technology in the past 10 years, the theory of using time to measure spatial displacement has been completed greatly. In the study of time grating, one novel linear displacement sensor is proposed based on the measurement principles of time grating. The measurement principles of linear displacement are similar to that of angular displacement. Both of them need one endless coordinate with uniform velocity. The theory of linear AC motor is used, and the three-phase winding with equal division space of 120° and three-phase exciting signal with uniform time are utilized to generate the endless moving coordinate with uniform velocity. The magnetic traveling wave arises from the left endpoint and disappears in the right endpoint, and it travels pole pitch distance of W during the periodic time of T with the uniform velocity. When magnetic traveling wave passes by the static probe and the moving probe, the electric signals will be induced on the winding, respectively. Therefore, the linear displacement can be achieved by comparing the phase between the two output induced signals from he static probe and the moving probe. Furthermore, in order to improve the machining technique, four kinds of winding framework are designed to employ. The experimental results show that advantages and disadvantages both exist in the design methods and the precision of experiment results reaches +/-2µm. The next study plan is to choose the most excellent design method through further experiments and improve the precision of displacement sensor greatly.

  3. Axial and transverse displacement tolerances during excimer laser surgery for myopia

    Shimmick, John K.; Munnerlyn, Charles R.; Clapham, Terrance N.; McDonald, Marguerite B.

    1991-06-01

    This paper presents an analysis of the effects of axial and transverse displacement on the optical quality and accuracy of lenses created during excimer laser photoablation. Tolerance levels for axial positioning of the cornea prior to and during surgery are presented. The axial tolerance levels are dependent upon a number of parameters which include the intended dioptric correction and laser system cone angle. A collimation lens is introduced as a means of desensitizing the laser system to axial displacement. Transverse displacement tolerances during laser treatment are shown to depend upon the treatment diameter, dioptric correction and acceptable distortion level in the lens ablated into the anterior corneal stroma. A video and computer analysis of transverse motion during seven randomly selected excimer laser refractive surgeries is presented. Although transverse displacement exceeded the tolerance levels presented, it did not appear to affect the quality of correction in the eight patients analyzed.

  4. Lesion size in relation to ablation site during radiofrequency ablation

    Petersen, H H; Chen, X; Pietersen, A;

    1998-01-01

    performed during two different flow-velocities in a tissue bath, while electrode contact pressure and position were unchanged. Target temperature was 80 degrees C. Obtained tip temperature, power consumption and lesion dimensions were measured. In vivo lesion volume, depth and width were found significantly...... convective cooling by induction of a flow around the electrode tip increases lesion dimensions and power consumptions. Furthermore we conclude that for the given target temperature the power consumption is positively correlated with lesion volume (p <0.001), whereas the obtained tip temperature is not.......This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation was...

  5. Ion acceleration enhanced by target ablation

    Laser proton acceleration can be enhanced by using target ablation, due to the energetic electrons generated in the ablation preplasma. When the ablation pulse matches main pulse, the enhancement gets optimized because the electrons' energy density is highest. A scaling law between the ablation pulse and main pulse is confirmed by the simulation, showing that for given CPA pulse and target, proton energy improvement can be achieved several times by adjusting the target ablation

  6. Field enhancement induced laser ablation

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob;

    Sub-diffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures...

  7. Laser ablation in analytical chemistry.

    Russo, Richard E; Mao, Xianglei; Gonzalez, Jhanis J; Zorba, Vassilia; Yoo, Jong

    2013-07-01

    In 2002, we wrote an Analytical Chemistry feature article describing the Physics of Laser Ablation in Microchemical Analysis. In line with the theme of the 2002 article, this manuscript discusses current issues in fundamental research, applications based on detecting photons at the ablation site (LIBS and LAMIS) and by collecting particles for excitation in a secondary source (ICP), and directions for the technology. PMID:23614661

  8. Ablative therapy for liver tumours

    Dick, E A; Taylor-Robinson, S D; Thomas, H C; Gedroyc, W M W

    2002-01-01

    Established ablative therapies for the treatment of primary and secondary liver tumours, including percutaneous ethanol injection, cryotherapy, and radiofrequency ablation, are discussed. Newer techniques such as magnetic resonance imaging guided laser interstitial thermal therapy of liver tumours has produced a median survival rate of 40.8 months after treatment. The merits of this newly emerging technique are discussed, together with future developments, such as focused ultrasound therapy, ...

  9. Percutaneous Ablation of Hepatic Tumors

    McCarley, James R.; Soulen, Michael C.

    2010-01-01

    The liver is a common site of both primary and secondary malignancy resulting in significant morbidity and mortality. Careful patient evaluation and triage allows for optimal utilization of all oncologic therapies, including radiation, systemic chemotherapy, surgery, transarterial therapies, and ablation. Although the role of interventional oncologists in the management of hepatic malignancies continues to evolve, the use of percutaneous ablation therapies has proven to be an effective and mi...

  10. Formation around planetary displaced orbit

    GONG Sheng-ping; LI Jun-feng; BAOYIN He-xi

    2007-01-01

    The paper investigates the relative motion around the planetary displaced orbit. Several kinds of displaced orbits for geocentric and martian cases were discussed. First, the relative motion was linearized around the displaced orbits. Then, two seminatural control laws were investigated for each kind of orbit and the stable regions were obtained for each case. One of the two control laws is the passive control law that is very attractive for engineering practice. However, the two control laws are not very suitable for the Martian mission. Another special semi-natural control law is designed based on the requirement of the Martian mission. The results show that large stable regions exist for the control law.

  11. Perceived Displacement explains Wolfpack Effect

    Matúš eŠimkovic

    2014-12-01

    Full Text Available We investigate the influence of perceived displacement of moving agent-like stimuli on the performance in dynamic interactive tasks. In order to reliably measure perceived displacement we utilize multiple tasks with different task demands. The perceived center of an agent’s body is displaced in the direction in which the agent is facing and this perceived displacement is larger than the theoretical position of the center of mass would predict. Furthermore, the displacement in the explicit judgment is dissociated from the displacement obtained by the implicit measures. By manipulating the location of the pivot point, we show that it is not necessary to postulate orientation as an additional cue utilized by perception, as has been suggested by earlier studies. These studies showed that the agent’s orientation influences the detection of chasing motion and the detection-related performance in interactive tasks. This influence has been labeled wolfpack effect. In one of the demonstrations of the wolfpack effect participants control a green circle on a display with a computer mouse. It has been shown that participants avoid display areas withagents pointing towards the green circle. Participants do so in favor of areas where the agents point in the direction perpendicular to the circle. We show that this avoidance behavior arises because the agent’s pivot point selected by the earlier studies is different from where people locate the center of agent’s body. As a consequence, the nominal rotation confounds rotation and translation. We show that the avoidance behavior disappears once the pivot point is set to the center of agent’s body.

  12. Esophageal papilloma: Flexible endoscopic ablation byradiofrequency

    Gianmattia del Genio; Federica del Genio; Pietro Schettino; Paolo Limongelli; Salvatore Tolone; Luigi Brusciano; Manuela Avellino; Chiara Vitiello; Giovanni Docimo; Angelo Pezzullo; Ludovico Docimo

    2015-01-01

    Squamous papilloma of the esophagus is a rare benignlesion of the esophagus. Radiofrequency ablation is anestablished endoscopic technique for the eradication ofBarrett esophagus. No cases of endoscopic ablation ofesophageal papilloma by radiofrequency ablation (RFA)have been reported. We report a case of esophagealpapilloma successfully treated with a single sessionof radiofrequency ablation. Endoscopic ablation ofthe lesion was achieved by radiofrequency using anew catheter inserted through the working channelof endoscope. The esophageal ablated tissue wasremoved by a specifically designed cup. Completeablation was confirmed at 3 mo by endoscopy withbiopsies. This case supports feasibility and safety of asa new potential indication for BarrxTM RFA in patientswith esophageal papilloma.

  13. DISPLACEMENT BASED SEISMIC DESIGN METHODS.

    HOFMAYER,C.MILLER,C.WANG,Y.COSTELLO,J.

    2003-07-15

    A research effort was undertaken to determine the need for any changes to USNRC's seismic regulatory practice to reflect the move, in the earthquake engineering community, toward using expected displacement rather than force (or stress) as the basis for assessing design adequacy. The research explored the extent to which displacement based seismic design methods, such as given in FEMA 273, could be useful for reviewing nuclear power stations. Two structures common to nuclear power plants were chosen to compare the results of the analysis models used. The first structure is a four-story frame structure with shear walls providing the primary lateral load system, referred herein as the shear wall model. The second structure is the turbine building of the Diablo Canyon nuclear power plant. The models were analyzed using both displacement based (pushover) analysis and nonlinear dynamic analysis. In addition, for the shear wall model an elastic analysis with ductility factors applied was also performed. The objectives of the work were to compare the results between the analyses, and to develop insights regarding the work that would be needed before the displacement based analysis methodology could be considered applicable to facilities licensed by the NRC. A summary of the research results, which were published in NUREGICR-6719 in July 2001, is presented in this paper.

  14. Local thermal ablation of renal cell carcinoma

    Purpose: With evolving local thermal ablation technology, the clinical application of thermal ablation has been actively investigated in the treatment for renal cell carcinoma. We review the evolution and current status of radiofrequency ablation and microwave ablation for renal cell carcinoma. Materials and methods: All articles published in English on radiofrequency ablation or microwave ablation as a treatment for renal cell carcinoma were identified with a MEDLINE® and PubMed® search from 1990 to 2010. Results: Local thermal ablation has several advantages, including keeping more normal renal units, relatively simple operation, easy tolerance, fewer complications, a shorter hospitalization and convalescence period. Long-term data has determined radiofrequency ablation is responsible for poor surgical candidates with renal cell carcinoma, however, tumor size, location and shape might affect the efficacy of radiofrequency ablation. Microwave ablation can induce large ablation volumes and yield good local tumor control. Associated complications appear to be low. Conclusions: Local ablative approaches seem to represent an attractive alternative to extirpative surgery for the treatment of small renal neoplasms in select patients. Potential developments include concepts to improve the accuracy and effectiveness of thermal ablation by improving the guiding, monitoring capabilities and detection capacity of multi-center lesions to provide at least equivalent cancer control to conventional surgery.

  15. CT imaging during microwave ablation: Analysis of spatial and temporal tissue contraction

    Purpose: To analyze the spatial distribution and temporal development of liver tissue contraction during high-temperature ablation by using intraprocedural computed tomography (CT) imaging. Methods: A total of 46 aluminum fiducial markers were positioned in a 60 × 45 mm grid, in a single plane, around a microwave ablation antenna in each of six ex vivo bovine liver samples. Ablations were performed for 10 min at 100 W. CT data of the liver sample were acquired every 30 s during ablation. Fiducial motion between acquisitions was tracked in postprocessing and used to calculate measures of tissue contraction and contraction rates. The spatial distribution and temporal evolution of contraction were analyzed. Results: Fiducial displacement indicated that the zone measured postablation was 8.2 ± 1.8 mm (∼20%) smaller in the radial direction and 7.1 ± 1.0 mm (∼10%) shorter in the longitudinal direction than the preablation tissue dimension. Therefore, the total ablation volume was reduced from its preablation value by approximately 45%. Very little longitudinal contraction was noted in the distal portion of the ablation zone. Central tissues contracted more than 60%, which was near an estimated limit of ∼70% based on initial water content. More peripheral tissues contracted only 15% in any direction. Contraction rates peaked during the first 60 s of heating with a roughly exponential decay over time. Conclusions: Ablation zones measured posttreatment are significantly smaller than the pretreatment tissue dimensions. Tissue contraction is spatially dependent, with the greatest effect occurring in the central ablation zone. Contraction rate peaks early and decays over time

  16. CT imaging during microwave ablation: Analysis of spatial and temporal tissue contraction

    Liu, Dong; Brace, Christopher L., E-mail: clbrace@wisc.edu [Departments of Radiology and Biomedical Engineering, University of Wisconsin, Madison, Wisconsin 53705 (United States)

    2014-11-01

    Purpose: To analyze the spatial distribution and temporal development of liver tissue contraction during high-temperature ablation by using intraprocedural computed tomography (CT) imaging. Methods: A total of 46 aluminum fiducial markers were positioned in a 60 × 45 mm grid, in a single plane, around a microwave ablation antenna in each of six ex vivo bovine liver samples. Ablations were performed for 10 min at 100 W. CT data of the liver sample were acquired every 30 s during ablation. Fiducial motion between acquisitions was tracked in postprocessing and used to calculate measures of tissue contraction and contraction rates. The spatial distribution and temporal evolution of contraction were analyzed. Results: Fiducial displacement indicated that the zone measured postablation was 8.2 ± 1.8 mm (∼20%) smaller in the radial direction and 7.1 ± 1.0 mm (∼10%) shorter in the longitudinal direction than the preablation tissue dimension. Therefore, the total ablation volume was reduced from its preablation value by approximately 45%. Very little longitudinal contraction was noted in the distal portion of the ablation zone. Central tissues contracted more than 60%, which was near an estimated limit of ∼70% based on initial water content. More peripheral tissues contracted only 15% in any direction. Contraction rates peaked during the first 60 s of heating with a roughly exponential decay over time. Conclusions: Ablation zones measured posttreatment are significantly smaller than the pretreatment tissue dimensions. Tissue contraction is spatially dependent, with the greatest effect occurring in the central ablation zone. Contraction rate peaks early and decays over time.

  17. Microwave ablation of hepatocellular carcinoma.

    Poggi, Guido; Tosoratti, Nevio; Montagna, Benedetta; Picchi, Chiara

    2015-11-01

    Although surgical resection is still the optimal treatment option for early-stage hepatocellular carcinoma (HCC) in patients with well compensated cirrhosis, thermal ablation techniques provide a valid non-surgical treatment alternative, thanks to their minimal invasiveness, excellent tolerability and safety profile, proven efficacy in local disease control, virtually unlimited repeatability and cost-effectiveness. Different energy sources are currently employed in clinics as physical agents for percutaneous or intra-surgical thermal ablation of HCC nodules. Among them, radiofrequency (RF) currents are the most used, while microwave ablations (MWA) are becoming increasingly popular. Starting from the 90s', RF ablation (RFA) rapidly became the standard of care in ablation, especially in the treatment of small HCC nodules; however, RFA exhibits substantial performance limitations in the treatment of large lesions and/or tumors located near major heat sinks. MWA, first introduced in the Far Eastern clinical practice in the 80s', showing promising results but also severe limitations in the controllability of the emitted field and in the high amount of power employed for the ablation of large tumors, resulting in a poor coagulative performance and a relatively high complication rate, nowadays shows better results both in terms of treatment controllability and of overall coagulative performance, thanks to the improvement of technology. In this review we provide an extensive and detailed overview of the key physical and technical aspects of MWA and of the currently available systems, and we want to discuss the most relevant published data on MWA treatments of HCC nodules in regard to clinical results and to the type and rate of complications, both in absolute terms and in comparison with RFA. PMID:26557950

  18. Femtosecond laser ablation of dentin

    The surface morphology, structure and composition of human dentin treated with a femtosecond infrared laser (pulse duration 500 fs, wavelength 1030 nm, fluences ranging from 1 to 3 J cm-2) was studied by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The average dentin ablation threshold under these conditions was 0.6 ± 0.2 J cm-2 and the ablation rate achieved in the range 1 to 2 µm/pulse for an average fluence of 3 J cm-2. The ablation surfaces present an irregular and rugged appearance, with no significant traces of melting, deformation, cracking or carbonization. The smear layer was entirely removed by the laser treatment. For fluences only slightly higher than the ablation threshold the morphology of the laser-treated surfaces was very similar to the dentin fracture surfaces and the dentinal tubules remained open. For higher fluences, the surface was more porous and the dentin structure was partially concealed by ablation debris and a few resolidified droplets. Independently on the laser processing parameters and laser processing method used no sub-superficial cracking was observed. The dentin constitution and chemical composition was not significantly modified by the laser treatment in the processing parameter range used. In particular, the organic matter is not preferentially removed from the surface and no traces of high temperature phosphates, such as the β-tricalcium phosphate, were observed. The achieved results are compatible with an electrostatic ablation mechanism. In conclusion, the high beam quality and short pulse duration of the ultrafast laser used should allow the accurate preparation of cavities, with negligible damage of the underlying material. (paper)

  19. Surgical Ablation of Atrial Fibrillation.

    Ramlawi, Basel; Abu Saleh, Walid K

    2015-01-01

    The Cox-maze procedure for the restoration of normal sinus rhythm, initially developed by Dr. James Cox, underwent several iterations over the years. The main concept consists of creating a series of transmural lesions in the right and left atria that disrupt re-entrant circuits responsible for propagating the abnormal atrial fibrillation rhythm. The left atrial appendage is excluded as a component of the Maze procedure. For the first three iterations of the Cox- maze procedure, these lesions were performed using a surgical cut-and-sew approach that ensured transmurality. The Cox-Maze IV is the most currently accepted iteration. It achieves the same lesion set of the Cox- maze III but uses alternative energy sources to create the transmural lesions, potentially in a minimally invasive approach on the beating heart. High-frequency ultrasound, microwave, and laser energy have all been used with varying success in the past. Today, bipolar radiofrequency heat or cryotherapy cooling are the most accepted sources for creating linear lesions with consistent safety and transmurality. The robust and reliable nature of these energy delivery methods has yielded a success rate reaching 90% freedom from atrial fibrillation at 12 months. Such approaches offer a significant long-term advantage over catheter-based ablation, especially in patients having longstanding, persistent atrial fibrillation with characteristics such as dilated left atrial dimensions, poor ejection fraction, and failed catheter ablation. Based on these improved results, there currently is significant interest in developing a hybrid ablation strategy that incorporates the superior transmural robust lesions of surgical ablation, the reliable stroke prevention potential of epicardial left atrial appendage exclusion, and sophisticated mapping and confirmatory catheter-based ablation technology. Such a minimally invasive hybrid strategy for ablation may lead to the development of multidisciplinary "Afib teams" to

  20. Microwave ablation of hepatocellular carcinoma

    2015-01-01

    Although surgical resection is still the optimal treatmentoption for early-stage hepatocellular carcinoma(HCC) in patients with well compensated cirrhosis,thermal ablation techniques provide a valid nonsurgicaltreatment alternative, thanks to their minimalinvasiveness, excellent tolerability and safety profile,proven efficacy in local disease control, virtuallyunlimited repeatability and cost-effectiveness. Differentenergy sources are currently employed in clinics asphysical agents for percutaneous or intra-surgicalthermal ablation of HCC nodules. Among them, radiofrequency(RF) currents are the most used, whilemicrowave ablations (MWA) are becoming increasinglypopular. Starting from the 90s', RF ablation (RFA) rapidlybecame the standard of care in ablation, especially inthe treatment of small HCC nodules; however, RFAexhibits substantial performance limitations in thetreatment of large lesions and/or tumors located nearmajor heat sinks. MWA, first introduced in the FarEastern clinical practice in the 80s', showing promisingresults but also severe limitations in the controllabilityof the emitted field and in the high amount of poweremployed for the ablation of large tumors, resultingin a poor coagulative performance and a relativelyhigh complication rate, nowadays shows better resultsboth in terms of treatment controllability and of overallcoagulative performance, thanks to the improvementof technology. In this review we provide an extensiveand detailed overview of the key physical and technicalaspects of MWA and of the currently available systems,and we want to discuss the most relevant published dataon MWA treatments of HCC nodules in regard to clinicalresults and to the type and rate of complications, both inabsolute terms and in comparison with RFA.

  1. Transhemangioma Ablation of Hepatocellular Carcinoma

    Radiofrequency ablation (RFA) is a well-established treatment modality in the treatment of early hepatocellular carcinoma (HCC) [1]. Safe trajectory of the RFA probe is crucial in decreasing collateral tissue damage and unwarranted probe transgression. As a percutaneous technique, however, the trajectory of the needle is sometimes constrained by the available imaging plane. The presence of a hemangioma beside an HCC is uncommon but poses the question of safety related to probe transgression. We hereby describe a case of transhemangioma ablation of a dome HCC.

  2. Transhemangioma Ablation of Hepatocellular Carcinoma

    Pua, Uei, E-mail: druei@yahoo.com [Tan Tock Seng Hospital, Department of Diagnostic Radiology (Singapore)

    2012-12-15

    Radiofrequency ablation (RFA) is a well-established treatment modality in the treatment of early hepatocellular carcinoma (HCC) [1]. Safe trajectory of the RFA probe is crucial in decreasing collateral tissue damage and unwarranted probe transgression. As a percutaneous technique, however, the trajectory of the needle is sometimes constrained by the available imaging plane. The presence of a hemangioma beside an HCC is uncommon but poses the question of safety related to probe transgression. We hereby describe a case of transhemangioma ablation of a dome HCC.

  3. PHASE CONVERTER OF COMPOSING DISPLACEMENT

    SMIRNOV YU.S.; Lysov, A. N.; E.V. Yurasova; SAFRONOV V.V.; VSTAVSKAYA E.V.

    2016-01-01

    Minimax strategy of mechatronic converters efficiency improving relative to error decrease with velocity increase at the same time provides common dataware level rise. The analysis of usage possibilities of different type position transducers (PT) gives the advantages of resolvers. The subsequent processing of their output signals is performed by “Resolver-to-Digit” Converter (RDC) which provides displacement digital equivalent and digital or analog signals specifying its velocity and acceler...

  4. Ablation of Solid Hydrogen in a Plasma

    Jørgensen, L. W.; Sillesen, Alfred Hegaard

    1979-01-01

    Several hydrogen pellet ablation models based on the formation of a shielding neutral cloud have been reported by different authors. The predicted ablation rates are shown to follow almost the same scaling law and this is used to explain the authors' ablation experiment....

  5. Soft thrombus formation in radiofrequency catheter ablation

    Demolin, JM; Eick, OJ; Munch, K; Koullick, E; Nakagawa, H; Wittkampf, FHM

    2002-01-01

    During RF catheter ablation, local temperature elevation can result in coagulum formation on the ablation electrode, resulting in impedance rise. A recent study has also demonstrated the formation of a so-called soft thrombus during experimental ablations. This deposit poorly adhered to the catheter

  6. Laser ablation at the hydrodynamic regime

    Gojani Ardian B.

    2013-01-01

    Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

  7. Harmonic motion imaging for abdominal tumor detection and high-intensity focused ultrasound ablation monitoring: an in vivo feasibility study in a transgenic mouse model of pancreatic cancer.

    Chen, Hong; Hou, Gary Y; Han, Yang; Payen, Thomas; Palermo, Carmine F; Olive, Kenneth P; Konofagou, Elisa E

    2015-09-01

    Harmonic motion imaging (HMI) is a radiationforce- based elasticity imaging technique that tracks oscillatory tissue displacements induced by sinusoidal ultrasonic radiation force to assess the resulting oscillatory displacement denoting the underlying tissue stiffness. The objective of this study was to evaluate the feasibility of HMI in pancreatic tumor detection and high-intensity focused ultrasound (HIFU) treatment monitoring. The HMI system consisted of a focused ultrasound transducer, which generated sinusoidal radiation force to induce oscillatory tissue motion at 50 Hz, and a diagnostic ultrasound transducer, which detected the axial tissue displacements based on acquired radio-frequency signals using a 1-D cross-correlation algorithm. For pancreatic tumor detection, HMI images were generated for pancreatic tumors in transgenic mice and normal pancreases in wild-type mice. The obtained HMI images showed a high contrast between normal and malignant pancreases with an average peak-to-peak HMI displacement ratio of 3.2. Histological analysis showed that no tissue damage was associated with HMI when it was used for the sole purpose of elasticity imaging. For pancreatic tumor ablation monitoring, the focused ultrasound transducer was operated at a higher acoustic power and longer pulse length than that used in tumor detection to simultaneously induce HIFU thermal ablation and oscillatory tissue displacements, allowing HMI monitoring without interrupting tumor ablation. HMI monitoring of HIFU ablation found significant decreases in the peak-to-peak HMI displacements before and after HIFU ablation with a reduction rate ranging from 15.8% to 57.0%. The formation of thermal lesions after HIFU exposure was confirmed by histological analysis. This study demonstrated the feasibility of HMI in abdominal tumor detection and HIFU ablation monitoring. PMID:26415128

  8. Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

    Hébert, H.; Vidal, F.; Martin, F.; Kieffer, J.-C.; Nadeau, A.; Johnston, T. W.; Blouin, A.; Moreau, A.; Monchalin, J.-P.

    2005-08-01

    We have investigated high-frequency ultrasound generated by single laser pulses in thin (50μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80fs and 270ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7J/cm2. For fluences greater than the ablation threshold (0.25 and 0.63J/cm2 for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed.

  9. Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

    We have investigated high-frequency ultrasound generated by single laser pulses in thin (50 μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80 fs and 270 ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7 J/cm2. For fluences greater than the ablation threshold (0.25 and 0.63 J/cm2 for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed

  10. Microstructure and properties of W-ZrC composites prepared by the displacive compensation of porosity (DCP) method

    Zhang Shouming, E-mail: shoumzh@163.com [Key Lab of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, DeYa Road, Changsha 410073 (China); Wang Song; Li Wei; Zhu Yulin; Chen Zhaohui [Key Lab of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, DeYa Road, Changsha 410073 (China)

    2011-08-18

    Highlights: > Microstructure of the W-ZrC composites was investigated using TEM and SEAD. > Mechanical properties of the composites were measured. > Ablation resistance was researched. - Abstract: Tungsten-zirconium carbide composites were fabricated at different temperatures by the displacive compensation of porosity (DCP) method, the microstructure, mechanical properties, and ablation resistance were investigated. It was found that no WC phase was left in the composites prepared at 1400 deg. C, and a few residual W{sub 2}C particles were surrounded in W product. Microstructure analyses revealed that zirconium atoms diffused into tungsten carbide to form ZrC and W{sub 2}Zr besides carbon diffused into the Zr{sub 2}Cu melt. Composites fabricated at 1400 deg. C had a flexural strength of 356.7 {+-} 15.2 MPa, an elastic modulus of 193.7 {+-} 9.8 GPa, a fracture toughness of 7.0 {+-} 0.7 MPa m{sup 1/2}, and a hardness of 13.6 {+-} 0.7 GPa. After ablated by an oxyacetylene flame for 30 s, the higher temperature prepared composites had a better ablation resistance, the linear ablation rate was 0.0033 {+-} 0.0004 mm/s, and the mass ablation rate was 0.0012 {+-} 0.0001 g/s.

  11. Radiofrequency ablation of liver metastases

    The liver is the second only to lymph nodes as the most common site of metastatic disease irrespective of the primary tumor. Up to 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improvement of the survival time, only approximately 20% of the patients are eligible for surgical intervention. Radiofrequency (RF) ablation represents one of the most important alternatives as well as complementary methods for the therapy of liver metastases. RF ablation can lead in a selected patient group to a palliation or to an increased life expectancy. RF ablation appears either safer (vs. cryotherapy) or easier (vs. laser) or more effective (percutaneous ethanol instillation [PEI]), transarterial chemoembolisation [TACE] in comparison with other minimal invasive procedures. RF ablation can be performed percutaneously, laparoscopically or intraoperatively and may be combined with chemotherapy as well as with surgical resection. Permanent technical improvements of RF systems, a better understanding of the underlying electrophysiological principles and an interdisciplinary approach will lead to a prognosis improvement in patients with liver metastases. (orig.)

  12. Modern Advances in Ablative TPS

    Venkatapathy, Ethiraj

    2013-01-01

    Topics covered include: Physics of Hypersonic Flow and TPS Considerations. Destinations, Missions and Requirements. State of the Art Thermal Protection Systems Capabilities. Modern Advances in Ablative TPS. Entry Systems Concepts. Flexible TPS for Hypersonic Inflatable Aerodynamic Decelerators. Conformal TPS for Rigid Aeroshell. 3-D Woven TPS for Extreme Entry Environment. Multi-functional Carbon Fabric for Mechanically Deployable.

  13. A numerical simulation of ablation controlled arcs

    Godin, D.; Trepanier, J.Y. [Ecole Polytechnique, Dept. of Mechanical Engineering, Montreal, PQ (Canada); Eby, S.D. [Ecole Polytechnique, Centre de Recherche en Calcul Applique, Montreal, PQ (Canada); Robin-Jouan, P. [GEC-Alsthom T and D, Villeurbanne, (France)

    1998-09-01

    An approach to model the ablation phenomenon of ablation controlled arcs using computational fluid dynamics was presented. Ablation controlled arcs are found in high voltage electrical equipment such as fuses and circuit-breakers. A qualitative prediction of the ablation level is critical from an industrial point of view because deliberate use of ablation is made to increase the pressure in a circuit-breaker chamber to allow for an efficient extinction when the current returns to zero. The numerical model was validated by comparing results of published experimental data. 7 refs., 10 figs.

  14. Technology and Structural Unemployment: Reemploying Displaced Adults.

    Congress of the U.S., Washington, DC. Office of Technology Assessment.

    This report concentrates on problems of displaced blue-collar and nonprofessional white-collar workers. Chapter 1 is a summary. Chapter 2 discusses policy issues and options focused on helping people prepare for worklife changes and helping workers to cope if displacement occurs. A definition and description of worker displacement are offered in…

  15. 25 CFR 700.59 - Displaced person.

    2010-04-01

    ... 25 Indians 2 2010-04-01 2010-04-01 false Displaced person. 700.59 Section 700.59 Indians THE... Policies and Instructions Definitions § 700.59 Displaced person. Displaced person means a member of the... residing within the area partitioned to the Hopi Tribe who must be relocated pursuant to the Act. This...

  16. Proof nets for the Displacement calculus

    Moot, Richard

    2016-01-01

    We present a proof net calculus for the Displacement calculus and show its correctness. This is the first proof net calculus which models the Displacement calculus directly and not by some sort of translation into another formalism. The proof net calculus opens up new possibilities for parsing and proof search with the Displacement calculus.

  17. Electromagnetic device of linear displacement

    The device moves a rod integral with a nuclear reactor control element. It has a grab for the rod operated by a mobil pole drive by a coil carried by a surrounding sealed casing, a second grab with fixed and mobile poles with facing surfaces shaped to limit the variation of magnetic force with distance between them, and a plunger driven by a coil to bear against another mobile pole moved by a coil. The invention proposes a device ensuring a displacement while the impact forces at the different level of the mechanism are reduced

  18. Displaced Children: The Psychological Implications.

    Joshi, Paramjit T; Fayyad, John A

    2015-10-01

    Millions of people across the world have been displaced or live in exile and/or as refugees largely as a consequence of wars, acts of terrorism, and catastrophic natural disasters. There are serious psychological consequences as a result of these extremely difficult life circumstances. Adults often can express their needs and have them be heard, whereas children are unable to do so. The children may be provided food, shelter, and clothing and have their medical needs attended to, but their emotional and psychological needs go unrecognized and unmet, with dire and monumental long-term consequences. PMID:26346385

  19. Microwave Ablation Compared with Radiofrequency Ablation for Breast Tissue in an Ex Vivo Bovine Udder Model

    Purpose: To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue. Materials and Methods: MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation. Results: The mean short-axis diameters of the coagulation zones were 1.34 ± 0.14, 1.45 ± 0.13, and 1.74 ± 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 ± 0.09 and 1.26 ± 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 ± 0.65, 2.85 ± 0.72, and 4.45 ± 0.47 cm3 for MW ablation at outputs of 25W, 35W, and 45W and 1.18 ± 0.30 and 2.29 ± 0.55 cm3 got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations. Conclusion: MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.

  20. Displacement of squeezed propagating microwave states

    Fedorov, Kirill G.; Zhong, Ling; Pogorzalek, Stefan; Eder, Peter; Fischer, Michael; Goetz, Jan; Wulschner, Friedrich; Xie, Edwar; Menzel, Edwin; Deppe, Frank; Marx, Achim; Gross, Rudolf

    Displacement of propagating squeezed states is a fundamental operation for quantum communications. It can be applied to fundamental studies of macroscopic quantum coherence and has an important role in quantum teleportation protocols with propagating microwaves. We generate propagating squeezed states using a Josephson parametric amplifier and implement displacement using a cryogenic directional coupler. We study single- and two-mode displacement regimes. For the single-mode displacement we find that the squeezing level of the displaced squeezed state does not depend on the displacement amplitude. Also, we observe that quantum entanglement between two spatially separated channels stays constant across 4 orders of displacement power. We acknowledge support by the German Research Foundation through SFB 631 and FE 1564/1-1, the EU project PROMISCE, and Elite Network of Bavaria through the program ExQM.

  1. Characterization of tracked radiofrequency ablation in phantom

    In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4±0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA

  2. Percutaneous thermal ablation of renal neoplasms

    Due to modern examination techniques such as multidetector computed tomography and high-field magnetic resonance imaging, the detection rate of renal neoplasms is continually increasing. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that are possible neoplasms should be treated. Traditional treatment techniques include radical nephrectomy or nephron-sparing resection, which are increasingly performed laparoscopically. Modern thermal ablation techniques such as hyperthermal techniques like radiofrequency ablation RFA, laser induced thermal ablation LITT, focused ultrasound FUS and microwave therapy MW, as well as hypothermal techniques (cryotherapy) may be a useful treatment option for patients who are unfit for or refuse surgical resection. Cryotherapy is the oldest and best known thermal ablation technique and can be performed laparoscopically or percutaneously. Since subzero temperatures have no antistyptic effect, additional maneuvers must be performed to control bleeding. Percutaneous cryotherapy of renal tumors is a new and interesting method, but experience with it is still limited. Radiofrequency ablation is the most frequently used method. Modern probe design allows volumes between 2 and 5 cm in diameter to be ablated. Due to hyperthermal tract ablation, the procedure is deemed to be safe and has a low complication rate. Although there are no randomized comparative studies to open resection, the preliminary results for renal RFA are promising and show RFA to be superior to other thermal ablation techniques. Clinical success rates are over 90% for both, cryo- and radiofrequency ablation. Whereas laser induced thermal therapy is established in hepatic ablation, experience is minimal with respect to renal application. For lesions of more than 2 cm in diameter, additional cooling catheters are required. MR thermometry offers temperature control during ablation. Microwave ablation is characterized by small ablation volumes

  3. A Theoretical Model to Predict Both Horizontal Displacement and Vertical Displacement for Electromagnetic Induction-Based Deep Displacement Sensors

    Xiong Li

    2011-12-01

    Full Text Available Deep displacement observation is one basic means of landslide dynamic study and early warning monitoring and a key part of engineering geological investigation. In our previous work, we proposed a novel electromagnetic induction-based deep displacement sensor (I-type to predict deep horizontal displacement and a theoretical model called equation-based equivalent loop approach (EELA to describe its sensing characters. However in many landslide and related geological engineering cases, both horizontal displacement and vertical displacement vary apparently and dynamically so both may require monitoring. In this study, a II-type deep displacement sensor is designed by revising our I-type sensor to simultaneously monitor the deep horizontal displacement and vertical displacement variations at different depths within a sliding mass. Meanwhile, a new theoretical modeling called the numerical integration-based equivalent loop approach (NIELA has been proposed to quantitatively depict II-type sensors’ mutual inductance properties with respect to predicted horizontal displacements and vertical displacements. After detailed examinations and comparative studies between measured mutual inductance voltage, NIELA-based mutual inductance and EELA-based mutual inductance, NIELA has verified to be an effective and quite accurate analytic model for characterization of II-type sensors. The NIELA model is widely applicable for II-type sensors’ monitoring on all kinds of landslides and other related geohazards with satisfactory estimation accuracy and calculation efficiency.

  4. Simplified method for esophagus protection during radiofrequency catheter ablation of atrial fibrillation - prospective study of 704 cases

    José Carlos Pachón Mateos

    2015-04-01

    Full Text Available AbstractIntroduction:Although rare, the atrioesophageal fistula is one of the most feared complications in radiofrequency catheter ablation of atrial fibrillation due to the high risk of mortality.Objective:This is a prospective controlled study, performed during regular radiofrequency catheter ablation of atrial fibrillation, to test whether esophageal displacement by handling the transesophageal echocardiography transducer could be used for esophageal protection.Methods:Seven hundred and four patients (158 F/546M [22.4%/77.6%]; 52.8±14 [17-84] years old, with mean EF of 0.66±0.8 and drug-refractory atrial fibrillation were submitted to hybrid radiofrequency catheter ablation (conventional pulmonary vein isolation plus AF-Nests and background tachycardia ablation with displacement of the esophagus as far as possible from the radiofrequency target by transesophageal echocardiography transducer handling. The esophageal luminal temperature was monitored without and with displacement in 25 patients.Results:The mean esophageal displacement was 4 to 9.1cm (5.9±0.8 cm. In 680 of the 704 patients (96.6%, it was enough to allow complete and safe radiofrequency delivery (30W/40ºC/irrigated catheter or 50W/60ºC/8 mm catheter without esophagus overlapping. The mean esophageal luminal temperature changes with versus without esophageal displacement were 0.11±0.13ºC versus 1.1±0.4ºC respectively, P<0.01. The radiofrequency had to be halted in 68% of the patients without esophageal displacement because of esophageal luminal temperature increase. There was no incidence of atrioesophageal fistula suspected or confirmed. Only two superficial bleeding caused by transesophageal echocardiography transducer insertion were observed.Conclusion:Mechanical esophageal displacement by transesophageal echocardiography transducer during radiofrequency catheter ablation was able to prevent a rise in esophageal luminal temperature, helping to avoid esophageal thermal

  5. Laser Ablation Molecular Isotopic Spectrometry

    Russo, Richard E., E-mail: rerusso@lbl.gov [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Applied Spectra, Inc., 46661 Fremont Boulevard, Fremont, CA 94538 (United States); Bol' shakov, Alexander A. [Applied Spectra, Inc., 46661 Fremont Boulevard, Fremont, CA 94538 (United States); Mao Xianglei [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); McKay, Christopher P. [NASA-Ames Research Center, Moffett Field, CA 94035 (United States); Perry, Dale L.; Sorkhabi, Osman [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2011-02-15

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method - LAMIS - can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  6. Laser Ablation Molecular Isotopic Spectrometry

    Russo, Richard E.; Bol'shakov, Alexander A.; Mao, Xianglei; McKay, Christopher P.; Perry, Dale L.; Sorkhabi, Osman

    2011-02-01

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method — LAMIS — can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  7. Tumor Ablation with Irreversible Electroporation

    Al-Sakere, Bassim; André, Franck,; Bernat, Claire; Connault, Elisabeth; Opolon, Paule; Davalos, Rafael V.; Rubinsky, Boris; Mir, Lluis M.

    2007-01-01

    We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop dur...

  8. Caries selective ablation: the handpiece

    Hennig, Thomas; Rechmann, Peter; Holtermann, Andreas

    1995-05-01

    Caries selective ablation is fixed to a window of fluences predicted by the ablation thresholds of carious and healthy dentin, respectively. The aim of the study was to develop a dental handpiece which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which acts in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium fall exactly into the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. Fluences are constant if the handpiece is used in contact mode or at a distance. Normally the surface of a bare fiber working in contact mode is destroyed after a few shots. Coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.

  9. Shore line displacement in Oeregrundsgrepen

    This report is a part of the SKB project 'SAFE' (Safety Assessment of the Final Repository of Radioactive Operational Waste). The aim of project SAFE is to update the previous safety analysis of SFR-1. The analysis is to be presented to the Swedish authorities not later than the end of 2000. SFR-1 is a facility for disposal of low and intermediate level radioactive waste and is situated in bedrock beneath the Baltic Sea, 1 km off the coast near the Forsmark nuclear power plant in Northern Uppland. The shore displacement in the Oeregrundsgrepen area is at present approximately 60 cm per 100 years and is slowly decreasing, but will still be substantial for many thousands of years. Since Oeregrundsgrepen is a relatively shallow part of the Bothnian Sea, the positive shore displacement will greatly effect the proportions of land and sea in the future. Within 2000 years (4000 AD) half of the current water area in Oeregrundsgrepen will be land and the water volume will be decreased with two thirds. At 7000 AD, the whole Oeregrundsgrepen area will be without brackish water. The effects on the landscape evolution due to shore displacement in the Oeregrundsgrepen area are illustrated in a chronological series of digital maps in Power Point format available saved on the supplied CD-rom and entitled 'Elevation.ppt '. The bedrock tectonics in the area are in two dominating directions: one northern that can be seen in the west shoreline of the island Graesoe and one in a north-westerly direction seen in the shoreline of the mainland. Many of the large basins that will be established in the area due to the shore displacement will be elongated in one of these directions. Some of the basins are relatively shallow and therefore probably will be totally filled with organic rich sediments and will form peat or bogs. Other basins, especially Graesoeraennan (the deep channel on the west side of Graesoe) are deep basins and will form a long chain of deep lakes. One of the deeper basins

  10. Polybenzimidazoles Via Aromatic Nucleophilic Displacement

    Connell, John W. (Inventor); Hergerrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1997-01-01

    Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenylbenzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl)benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl)benzimidazoles are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  11. Searching for Displaced Higgs Decays

    Csaki, Csaba; Lombardo, Salvator; Slone, Oren

    2015-01-01

    We study a simplified model of the SM Higgs boson decaying to a degenerate pair of scalars which travel a macroscopic distance before decaying to SM particles. This is the leading signal for many well-motivated solutions to the hierarchy problem that do not propose additional light colored particles. Bounds for displaced Higgs decays below $10$ cm are found by recasting existing tracker searches from Run I. New tracker search strategies, sensitive to the characteristics of these models and similar decays, are proposed with sensitivities projected for Run II at $\\sqrt{s} = 13 $ TeV. With 20 fb$^{-1}$ of data, we find that Higgs branching ratios down to $7 \\times 10^{-4}$ can be probed for centimeter decay lengths.

  12. Polyimidazoles via aromatic nucleophilic displacement

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor)

    1992-01-01

    Polyimidazoles (PI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl) imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethyl acetamide, sulfolane, N-methylpyrrolidinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. The di(hydroxyphenyl) imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl) imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxphenyl) imidazole monomer. This synthetic route has provided high molecular weight PI of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

  13. Possible displacement of mercury's dipole

    Earlier attempts to model the Hermean magnetospheric field based on a planet-centered magnetic multipole field have required the addition of a quadrupole moment to obtain a good fit to space vehicle observations. In this work we obtain an equally satisfactory fit by assuming a null quadrupole moment and least squares fitting of the displacement of the planetary dipole from the center of the planet. We find a best fit for a dipole displacement from the planet center of 0.033 R/sub m/ away from the solar direction, 0.025 R/sub m/ toward dawn in the magnetic equatorial plane, and 0.189 R/sub m/ northward along the magnetic dipole axis, where R/sub m/ is the planet radius. Therefore the presence of a magnetic quadrupole moment is not ruled out. The compressed dipole field more completely represents the field in the present work than in previous work where the intrinsic quadrupole field was not included in the magnetopause surface and field calculations. Moreover, we have corrected a programing error in previous work in the computation of dipole tilt lambda away from the sun. We find a slight increase for the planet dipole moment of 190γR/sub m/3 and a dipole tilt angle lambda away from the sun. We find a slight increase for the planet moment of 190γR/sub m/3 and a dipole tilt angle lambda of only 1.20 away from the sun. All other parameters are essentially unchanged

  14. Transient Ablation Regime in Circuit Breakers

    Alexandre, Martin; Jean-Yves, Trepanier; Marcelo, Reggio; Guo, Xueyan

    2007-12-01

    Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers. The simplified ablation model used in litterature has been updated to take into account the unsteady state of ablation. Ablation rate and velocity are now calculated by a kinetic model using two layers of transition, between the bulk plasma and the ablating wall. The first layer (Knudsen layer), right by the wall, is a kinetic layer of a few mean-free path of thickness. The second layer is collision dominated and makes the transition between the kinetic layer and the plasma bulk. With this new coupled algorithm, it is now possible to calculate the temperature distribution inside the wall, as well as more accurate ablation rates.

  15. Explosive character of the atheroma plaques ablation

    At the present time, ischemia (heart disease) is a main cause of the death in the world; a promising method for its treatment is the use of the technology of the laser light of raised power for the ablation of the atherosclerosis plaques. In this paper, the thermodynamic processes will be studied at the beginning and during atheroma ablation using Nd-YAG (10-50 w) and Argon (4-10 w) lasers of a theoretical point of view. The spatial distribution of the temperature during the ablation has been modelated by the method of finite volumes. The manifestation of the raised temperature of the tissue at the threshold of the ablation, which describes the explosive nature of the ablation by laser (popcorn effect), is observed and discussed. The results indicate the quantitative differences in the ablation behavior between the two used lasers, which can have important clinical implications particularly in the reduction of thermal damages to surrounding normal tissue. (author)

  16. Radiofrequency Ablation of Hepatic Cysts : Case Report

    Radiofrequency ablation has been frequently performed on intra-hepatic solid tumor, namely, hepatocellular carcinoma, metastatic tumor and cholangio carcinoma, for take the cure. But, the reports of radiofrequency ablation for intrahepatic simple cysts are few. In vitro experiment of animal and in vivo treatment for intrahepatic cysts of human had been reported in rare cases. We report 4 cases of radiofrequency ablation for symptomatic intrahepatic cysts

  17. Photoacoustic Characterization of Radiofrequency Ablation Lesions

    Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

    2012-01-01

    Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh ...

  18. Moderne Technologien in der Ablation des Vorhofflimmerns

    Haegeli, L; Duru, F.; Lüscher, T F

    2010-01-01

    Catheter ablation for atrial fibrillation has become an accepted therapy. The arrhythmia affects around 6% of the population over the age of 65 years. Electrical isolation of the pulmonary veins from the left atrium is the central strategy in catheter ablation for paroxysmal atrial fibrillation. However, procedural outcomes and efficacy using sequential “point-by-point” radiofrequency lesion creation with a conventional ablation catheter are operator-dependent and time-consuming. Moreover, re...

  19. Computer-aided hepatic tumour ablation

    Voirin, D; Amavizca, M; Leroy, A; Letoublon, C; Troccaz, J; Voirin, David; Payan, Yohan; Amavizca, Miriam; Leroy, Antoine; Letoublon, Christian; Troccaz, Jocelyne

    2001-01-01

    Surgical resection of hepatic tumours is not always possible. Alternative techniques consist in locally using chemical or physical agents to destroy the tumour and this may be performed percutaneously. It requires a precise localisation of the tumour placement during ablation. Computer-assisted surgery tools may be used in conjunction to these new ablation techniques to improve the therapeutic efficiency whilst benefiting from minimal invasiveness. This communication introduces the principles of a system for computer-assisted hepatic tumour ablation.

  20. Cardiac Remodeling After Atrial Fibrillation Ablation

    Li-Wei Lo, MD; Shih-Ann Chen, MD

    2013-06-01

    Full Text Available Radiofrequency catheter ablation procedures are considered a reasonable option for patients with symptomatic, drug refractory atrial fibrillation (AF. Ablation procedures have been reported to effectively restore sinus rhythm and provide long-term relief of symptoms. Both electrical and structural remodeling occurs with AF. A reversal of the electrical remodeling develops within 1 week after restoration to sinus rhythm following the catheter ablation. The recovery rate is faster in the right atrium than the left atrium. Reverse structural remodeling takes longer and is still present 2 to 4 months after restoration of sinus rhythm. The left atrial transport function also improves after successful catheter ablation of AF. Left atrial strain surveys from echocardiography are able to identify patients who respond to catheter ablation with significant reverse remodeling after ablation. Pre-procedural delayed enhancement magnetic resonance imaging is also able to determine the degree of atrial fibrosis and is another tool to predict the reverse remodeling after ablation. The remodeling process is complex if recurrence develops after ablation. Recent evidence shows that a combined reverse electrical and structural remodeling occurs after ablation of chronic AF when recurrence is paroxysmal AF. Progressive electrical remodeling without any structural remodeling develops in those with recurrence involving chronic AF. Whether progressive atrial remodeling is the cause or consequence during the recurrence of AF remains obscure and requires further study.

  1. Aromatic Thermosetting Copolyesters for Ablative TPS Project

    National Aeronautics and Space Administration — Better performing ablative thermal protection systems than currently available are needed to satisfy requirements of the most severe crew exploration vehicles, such...

  2. Plasma-mediated ablation of biofilm contamination

    Guo, Zhixiong; Wang, Xiaoliang; Huang, Huan

    2010-12-01

    Ultra-short pulsed laser removal of thin biofilm contamination on different substrates has been conducted via the use of plasma-mediated ablation. The biofilms were formed using sheep whole blood. The ablation was generated using a 1.2 ps ultra-short pulsed laser with wavelength centered at 1552 nm. The blood contamination was transformed into plasma and collected with a vacuum system. The single line ablation features have been measured. The ablation thresholds of blood contamination and bare substrates were determined. It is found that the ablation threshold of the blood contamination is lower than those of the beneath substrates including the glass slide, PDMS, and human dermal tissues. The ablation effects of different laser parameters (pulse overlap rate and pulse energy) were studied and ablation efficiency was measured. Proper ablation parameters were found to efficiently remove contamination with maximum efficiency and without damage to the substrate surface for the current laser system. Complete removal of blood contaminant from the glass substrate surface and freeze-dried dermis tissue surface was demonstrated by the USP laser ablation with repeated area scanning. No obvious thermal damage was found in the decontaminated glass and tissue samples.

  3. Modelling toehold-mediated RNA strand displacement

    Šulc, Petr; Romano, Flavio; Doye, Jonathan P K; Louis, Ard A

    2014-01-01

    We study the thermodynamics and kinetics of an RNA toehold-mediated strand displacement reaction with a recently developed coarse-grained model of RNA. Strand displacement, during which a single strand displaces a different strand previously bound to a complementary substrate strand, is an essential mechanism in active nucleic acid nanotechnology and has also been hypothesized to occur in vivo. We study the rate of displacement reactions as a function of the length of the toehold and temperature and make two experimentally testable predictions: that the displacement is faster if the toehold is placed at the 5' end of the substrate and that the displacement slows down with increasing temperature for longer toeholds.

  4. Rock displacements measured during URL shaft sinking

    During sinking of the Canadian Underground Research Laboratory (URL) shaft, borehole extensometers were used to obtain rock displacement measurements and a tape extensometer was used to measure total convergences. The instruments, instrument modifications, and methods used are described. The measurements are summarized and assessed, with particular emphasis on the influence of natural fractures on rock-mass response and the performance of the instrumentation. Displacements varied from 0.09 mm to 1.75 mm. The frequency of sub-vertical fractures in the rock appeared to be the main factor causing the variation in the measured displacements. Although the displacement instrumentation met certain operational requirement well, lack of precision was a problem. Displacement instrumentation used in future URL experiments should have more measuring points, greater sensitivity, and greater accuracy to better measure small displacements

  5. Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

    Wu, Po-hung; Brace, Chris L.

    2016-08-01

    Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm‑1), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm‑1) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm‑1). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility

  6. Preventing re-displacement through genuine reintegration in Burundi

    Lucy Hovil

    2012-12-01

    Full Text Available Displacement is often part of a cyclical process of conflict anddisplacement. Preventing displacement, therefore, is not only aboutpreventing new displacement but about ensuring that people do notget re-displaced.

  7. Policies for Displaced Workers: An American Perspective

    O'Leary, Christopher J.

    2009-01-01

    American employment policy for displaced workers started in the Great Depression with programs for the employment service, unemployment insurance, work experience, and direct job creation. Assistance for workers displaced by foreign competition emerged in the 1960s along with formalized programs for occupational job skill training. The policy focus on displaced workers was sharpened in the 1980s through the Worker Adjustment and Retraining Notification Act and the Economic Dislocation and Wor...

  8. Displacement speeds in turbulent premixed flame simulations

    Day, Marcus S.; Shepherd, Ian G.; Bell, J.; Grcar, Joseph F.; Lijewski, Michael J.

    2007-07-01

    The theory of turbulent premixed flames is based on acharacterization of the flame as a discontinuous surface propagatingthrough the fluid. The displacement speed, defined as the local speed ofthe flame front normal to itself, relative to the unburned fluid,provides one characterization of the burning velocity. In this paper, weintroduce a geometric approach to computing displacement speed anddiscuss the efficacy of the displacement speed for characterizing aturbulent flame.

  9. Displacing AIDS: therapeutic transitions in Northern Uganda

    Wilhelm-Solomon, M. M.; Alexander, Jocelyn; Daley, Patricia

    2014-01-01

    This doctoral project, entitled 'Displacing AIDS: Therapeutic Transitions in Northern Uganda' examines the biosocial transitions engendered by the treatment of HIV, focusing on antiretroviral therapy (ART/ARV) interventions, and the ways these are intertwined with the social transitions of conflict, displacement and return. The research involved an inter-disciplinary qualitative study with internally displaced communities living with HIV in northern Uganda, during 10 months fieldwork between ...

  10. Displacement of Propagating Squeezed Microwave States.

    Fedorov, Kirill G; Zhong, L; Pogorzalek, S; Eder, P; Fischer, M; Goetz, J; Xie, E; Wulschner, F; Inomata, K; Yamamoto, T; Nakamura, Y; Di Candia, R; Las Heras, U; Sanz, M; Solano, E; Menzel, E P; Deppe, F; Marx, A; Gross, R

    2016-07-01

    Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments, we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states remains constant over a wide range of the displacement power. PMID:27447495

  11. Displacement of Propagating Squeezed Microwave States

    Fedorov, Kirill G.; Zhong, L.; Pogorzalek, S.; Eder, P.; Fischer, M.; Goetz, J.; Xie, E.; Wulschner, F.; Inomata, K.; Yamamoto, T.; Nakamura, Y.; Di Candia, R.; Las Heras, U.; Sanz, M.; Solano, E.; Menzel, E. P.; Deppe, F.; Marx, A.; Gross, R.

    2016-07-01

    Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments, we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states remains constant over a wide range of the displacement power.

  12. Tracking speckle displacement by double Kalman filtering

    Donghui Li; Li Guo

    2006-01-01

    @@ A tracking technique using two sequentially-connected Kalman filter for tracking laser speckle displacement is presented. One Kalman filter tracks temporal speckle displacement, while another Kalman filter tracks spatial speckle displacement. The temporal Kalman filter provides a prior for the spatial Kalman filter, and the spatial Kalman filter provides measurements for the temporal Kalman filter. The contribution of a prior to estimations of the spatial Kalman filter is analyzed. An optical analysis system was set up to verify the double-Kalman-filter tracker's ability of tracking laser speckle's constant displacement.

  13. Increase in Volume of Ablation Zones during Follow-up Is Highly Suggestive of Ablation Site Recurrence in Colorectal Liver Metastases Treated with Radiofrequency Ablation

    Kele, Petra G.; de Jong, Koert P.; van der Jagt, Eric J.

    2012-01-01

    Purpose: To test the hypothesis that volume changes of ablation zones (AZs) on successive computed tomography (CT) scans could predict ablation site recurrences (ASRs) in patients with colorectal liver metastases treated by radiofrequency (RF) ablation. Materials and Methods: RF ablation was perform

  14. Therapeutic efficacy of percutaneous radiofrequency ablation versus microwave ablation for hepatocellular carcinoma.

    Lei Zhang

    Full Text Available The aim of this study was to investigate the therapeutic efficacy of percutaneous radiofrequency (RF ablation versus microwave (MW ablation for hepatocellular carcinoma (HCC measuring ≤ 5 cm in greatest diameter. From January 2006 to December 2006, 78 patients had undergone RF ablation whereas 77 had undergone MW ablation. Complete ablation (CA, local tumour progression (LTP and distant recurrence (DR were compared. The overall survival curves were calculated with the Kaplan-Meier technique and compared with the log-rank test. The CA rate was 83.4% (78/93 for RF ablation and 86.7%(91/105 for MW ablation. The LTP rate was 11.8% (11/93 for RF ablation and 10.5% (11/105 for MW ablation. DR was found in 51 (65.4% in the RF ablation and 62 (80.5% in the MW ablation. There was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.780 and the 1-, 3-, and 5-year disease-free survival rates (P = 0.123 between RF and MW ablation. At subgroup analyses, for patients with tumors ≤ 3.0 cm, there was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.067 and the corresponding disease-free survival rates(P = 0.849. For patients with tumor diameters of 3.1-5.0 cm, the 1-, 3-, and 5-year overall survival rates were 87.1%, 61.3%, and 40.1% for RF ablation and 85.4%, 36.6%, and 22% for MW ablation, with no significant difference (P = 0.068. The corresponding disease-free survival rates were 74.2%, 54.8%, and 45.2% for the RF ablation group and 53.3%, 26.8%, and 17.1% for the MW ablation group. The disease-free survival curve for the RF ablation group was significantly better than that for the MW ablation group (P = 0.018. RF ablation and MW ablation are both effective methods in treating hepatocellular carcinomas, with no significant differences in CA, LTP, DR, and overall survival.

  15. Effects of Fault Displacement on Emplacement Drifts

    The purpose of this analysis is to evaluate potential effects of fault displacement on emplacement drifts, including drip shields and waste packages emplaced in emplacement drifts. The output from this analysis not only provides data for the evaluation of long-term drift stability but also supports the Engineered Barrier System (EBS) process model report (PMR) and Disruptive Events Report currently under development. The primary scope of this analysis includes (1) examining fault displacement effects in terms of induced stresses and displacements in the rock mass surrounding an emplacement drift and (2 ) predicting fault displacement effects on the drip shield and waste package. The magnitude of the fault displacement analyzed in this analysis bounds the mean fault displacement corresponding to an annual frequency of exceedance of 10-5 adopted for the preclosure period of the repository and also supports the postclosure performance assessment. This analysis is performed following the development plan prepared for analyzing effects of fault displacement on emplacement drifts (CRWMS M and O 2000). The analysis will begin with the identification and preparation of requirements, criteria, and inputs. A literature survey on accommodating fault displacements encountered in underground structures such as buried oil and gas pipelines will be conducted. For a given fault displacement, the least favorable scenario in term of the spatial relation of a fault to an emplacement drift is chosen, and the analysis is then performed analytically. Based on the analysis results, conclusions are made regarding the effects and consequences of fault displacement on emplacement drifts. Specifically, the analysis will discuss loads which can be induced by fault displacement on emplacement drifts, drip shield and/or waste packages during the time period of postclosure

  16. Laparoscopic Radiofrequency Thermal Ablation for Uterine Adenomyosis

    Scarperi, Stefano; Pontrelli, Giovanni; Campana, Colette; Steinkasserer, Martin; Ercoli, Alfredo; Minelli, Luca; Bergamini, Valentino; Ceccaroni, Marcello

    2015-01-01

    Background and Objectives: Symptomatic uterine adenomyosis, unresponsive to medical therapy, is a challenging condition for patients who desire to preserve their uterus. This study was an evaluation of the feasibility and efficacy of laparoscopic radiofrequency thermal ablation of symptomatic nodular uterine adenomyosis. Methods: Fifteen women with symptomatic nodular adenomyosis, who had no plans for pregnancy but declined hysterectomy, underwent radiofrequency thermal ablation. Ultrasonogra...

  17. Time-stepping for laser ablation

    Harihar Khanal; David Autrique; Vasilios Alexiades

    2013-01-01

    Nanosecond laser ablation is a popular technique, applied in many areas of science and technology such as medicine, archaeology, chemistry, environmental and materials sciences. We outline a computational model for radiative and collisional processes occurring during ns-laser ablation, and compare the performance of various low and high order time-stepping algorithms.

  18. PULSED LASER ABLATION OF CEMENT AND CONCRETE

    Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

  19. Testing and evaluation of light ablation decontamination

    This report details the testing and evaluation of light ablation decontamination. It details WINCO contracted research and application of light ablation efforts by Ames Laboratory. Tests were conducted with SIMCON (simulated contamination) coupons and REALCON (actual radioactive metal coupons) under controlled conditions to compare cleaning effectiveness, speed and application to plant process type equipment

  20. Attitudes Towards Catheter Ablation for Atrial Fibrillation

    Vadmann, Henrik; Pedersen, Susanne S; Nielsen, Jens Cosedis;

    2015-01-01

    BACKGROUND: Catheter ablation for atrial fibrillation (AF) is an important but expensive procedure that is the subject of some debate. Physicians´ attitudes towards catheter ablation may influence promotion and patient acceptance. This is the first study to examine the attitudes of Danish...

  1. High Heat Flux Block Ablator-in-Honeycomb Heat Shield Using Ablator/Aerogel-Filled Foam Project

    National Aeronautics and Space Administration — Ultramet and ARA Ablatives Laboratory previously developed and demonstrated advanced foam-reinforced carbon/phenolic ablators that offer substantially increased...

  2. Regional resilience to displacements: Explaining the regional capacity to re-employ displaced workers

    Nyström, Kristina

    2015-01-01

    Job displacement, which is defined as an involuntary loss of job due to economic downturns or structural changes, hit millions of workers each year. According to OECD (2013) 2-7 percent of workers are displaced every year. For Sweden, OECD (2013) reports an average displacement rate of about 2 percent for the period 2000-2008. Our knowledge on the individual consequences of displacement, in terms of, for example, unemployment duration, and earning losses is comprehensive (See e.g. Hammermesh ...

  3. Etiopathogenesis of abomasal displacement in cattle

    Šamanc Horea

    2003-01-01

    Full Text Available Abomasal displacement presents topographic gastropathy, where this organ has changed its position, and there is simultaneous dilatation which can vary in intensity. The incidence of this disorder in herds of high-yield dairy cows varies to a great degree (1 to 18 %. Abomasal displacement was established in herds of East-Frisian cows in 1 to 3% animals, and in Holstein cow herds in 5 to 18 % animals. The most frequent abomasal displacement is to the left (88%. There is significant seasonal variation in the incidence of abomasal displacement. About two-thirds of cases of abomasal displacement are diagnosed from October until April. The disorder appears more frequently in cows with repeated lactations. It has been established that it appears after the first calving in 27.8% cases, after the second to fifth calving in 66.7% cases, and after the sixth and seventh calving in 5.5% of the cows. The response of endocrine pancreas B-cells for insulin secretion to hyperglycaemia caused by applying an excess-glucose test is reduced in cows with left abomasal displacement, and there is constant hyperglycaemia in cows with right abomasal displacement. The excess-glucose test indicates a disrupted function of the endocrine pancreas in diseased animals. It has been determined through examinations of Aml genotypes in Holstein cow herds in connection with the appearance of abomasal displacement, that the occurrence of this disorder cannot be attributed to a genetic predisposition.

  4. 40 CFR 205.153 - Engine displacement.

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Engine displacement. 205.153 Section 205.153 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) NOISE ABATEMENT PROGRAMS TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS Motorcycles § 205.153 Engine displacement. (a)...

  5. Video Games, Adolescents, and the Displacement Effect

    Fisher, Carla Christine

    2012-01-01

    The displacement effect (the idea that time spent in one activity displaces time spent in other activities) was examined within the lens of adolescents' video game use and their time spent reading, doing homework, in physically active sports and activities, in creative play, and with parents and friends. Data were drawn from the Panel Study…

  6. Capacitive Displacement Sensor With Frequency Readout

    Fritsch, Klaus

    1989-01-01

    Simple displacement-measuring circuit senses capacitance between two parallel conducting plates and produces output signal, with frequency proportional to distance between plates. Principle of circuit provides advantages over other methods because of frequency-encoded output and high linearity. Used to measure displacements.

  7. Fractal dimensionality of cascades of atomic displacements

    The cascades of opening displacements, formed during irradiation of solids are the most typical process of dissipation of the energy of incident particles and the generation of radiation defects. The aim of the present work is the examination of the energy dependence of the fractal dimensionality of the cascades of atomic displacements in the solid

  8. New Technologies in Atrial Fibrillation Ablation

    John Rickard, MD, MPH; Saman Nazarian MD, PhD

    2014-08-01

    Full Text Available Atrial fibrillation (AF is a major public health issue worldwide the incidence of which is likely to continue to rise. With the birth of pulmonary vein isolation(PVI, cardiac ablation has emerged as key strategy for the treatment of AF. PVI using traditional point by point radiofrequency ablation is time consuming and technically challenging. Refining patient selection for PVI also remains an important goal. New ablative strategies using catheter-based balloon technologies, such as cryothermy and laser-based systems, may simplify PVI. In addition, new MRI-based techniques offer the hope of refining patient selection prior to ablation. Lastly, FIRM mapping represents an entirely new approach to AF ablation via the targeting of mechanisms that perpetuate AF rather than simply targeting triggers alone.

  9. Phased RF ablation: results and concerns

    Alexandra Kiss, MD, PhD; G�bor S�ndorfi, MD; Edina Nagy-Bal�, MD, PhD; Mihran Martirosyan, MD; Zoltan Csanadi, MD, PhD

    2015-06-01

    Full Text Available reatment of atrial fibrillation (AF with catheter ablation has proven to be a safe and effective treatment modality which is offered to an increasing number of patients in many centers. Pulmonary vein isolation (PVI is an established cornerstone of AF ablation strategies. Athough the isolation of the pulmonary veins (PVs with irrigated focal radiofrequency (RF catheters using a point-by-point method is considered as the gold standard, it can be challenging to create contiguous lesions, time consuming, and require advanced three dimensional (3D mapping and navigational systems. The phased RF ablation system was designed to address many of these challenges associated with conventional focal RF ablation. In this review, we describe the main features of phased RF ablation and summarize the data available on clinical outcome with this technology.

  10. Tumor ablation with irreversible electroporation.

    Bassim Al-Sakere

    Full Text Available We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 micros at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%, in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation.

  11. Ablation with a single micropatterned KrF laser pulse: quantitative evidence of transient liquid microflow driven by the plume pressure gradient at the surface of polyesters

    Weisbuch, F.; Tokarev, V. N.; Lazare, S.; Débarre, D.

    A microscopic flow of a transient liquid film produced by KrF laser ablation is evidenced on targets of PET and PEN. Experiments were done by using single pulses of the excimer laser beam micropatterned with the aid of submicron projection optics and grating masks. The samples of various crystalline states, ablated with a grating-forming beam (period Λ=3.7 μm), were precisely measured by atomic force microscopy, in order to evidence any deviation from the ablation behavior predicted by the current theory (combination of ablation curve and beam profile). This was confirmed by comparing various behaviors dependent on the polymer nature (PC, PET and PEN). PC is a normally ablating polymer in the sense that the ablated profile can be predicted with previous theory neglecting liquid-flow effects. This case is called `dry' ablation and PC is used as a reference material. But, for some particular samples like crystalline PET, it is revealed that during ablation a film of transient liquid, composed of various components, which are discussed, can flow under the transient action of the gradient of the pressure of the ablation plume and resolidify at the border of the spot after the end of the pulse. This mechanism is further supported by a hydrodynamics theoretical model in which a laser-induced viscosity drop and the gradient of the plume pressure play an important role. The volume of displaced liquid increases with fluence (0.5 to 2 J/cm2) and satisfactory quantitative agreement is obtained with the present model. The same experiment done on the same PET polymer but prepared in the amorphous state does not show microflow, and such an amorphous sample behaves like the reference PC (`dry' ablation). The reasons for this surprising result are discussed.

  12. Boundary conditions for 3D dynamic models of ablation of ceramics by pulsed mid-infrared lasers

    Vila Verde, A. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Ramos, Marta M.D. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)]. E-mail: marta@fisica.uminho.pt

    2005-07-15

    We present and discuss a set of boundary conditions (BCs) to use in three-dimensional, mesoscopic, finite element models of mid-infrared pulsed laser ablation of brittle materials. These models allow the study of the transient displacement and stress fields generated at micrometer scales during and after one laser pulse, where using conventional BCs may lead to some results without physical significance that can be considered an artefact of the calculations. The proposed BCs are tested and applied to a micrometer-scale continuous model of human dental enamel under CO{sub 2} radiation (10.6 {mu}m, 0.35 {mu}s pulse, sub-ablative fluence), giving rise to the following results: the highest stress is obtained at the irradiated surface of the model, at the end of the laser pulse, but afterwards it decreases rapidly until it becomes significantly lower than the stress in a region 2.5 {mu}m deep in the model; a thermally induced vibration in the material is predicted. This non-intuitive dynamics in stress and displacement distribution cannot be neglected and has to be considered in dynamic laser ablation models, since it may have serious implications in the mechanisms of ablation.

  13. Rotor Displacement of the Ultrasonic Motor Having an Angular Displacement Self-Correction Function

    Chen, Xiaoduo; Kusakabe, Chiharu; Tomikawa, Yoshiro; Takano, Takehiro

    1993-09-01

    This paper deals with the experimental investigation for confirmation of rotor displacement of the ultrasonic stepping motor having an angular displacement self-correction function. The experiment focused on the relationship between the rotor’s vibration displacement and its staying position for the self-correction. The result proved that the rotor always stays at the position where the displacement is smallest by cutting a slit into the rotor. Moreover, it has also been found that the stable self-correction of rotor angular displacement depends upon both the rotor driving frequency and rotor clamping force.

  14. A model of pellet ablation with a multi-species ablatant

    The single species neutral - shielding model for the ablation of a hydrogenic pellet is extended by considering the ablatant as a mixture of four species: Molecular and atomic hydrogen, protons and electrons. Compared with the single-species-ablatant model, results of the analysis showed that the ablatant state differs considerably. The attenuation of the incoming electron energy and energy flux, however, are very much similar, irrespective of the ablatant composition. The scaling law of the pellet ablation rate with respect to the plasma state of Te, ne and the pellet radius, rp remains the same; the ablation rate is reduced approximately by 15%. At some combinations of Te, ne and rp, a weak shock can appear when the ablated flow downstream becomes sonic. A sufficient but not necessary condition for its occurrence is that the ablatant approaches either a state of complete dissociation, or complete ionization. To study the possible existence of an effective energy absorbing spherical region around the pellet, a comparison between the local ablated electron collisional mean free path and the electron Larmor radius in the cloud is made. A critical field, Bc is then defined and evalued at the ionization radius, ri. For plasma state of fusion interest and pellet radius beyond 0.15 mm, Bc is well above 10 Tesla. (orig.) With 3 tabs., 7 figs., 21 refs

  15. Neural Ablation and Regeneration in Pain Practice.

    Choi, Eun Ji; Choi, Yun Mi; Jang, Eun Jung; Kim, Ju Yeon; Kim, Tae Kyun; Kim, Kyung Hoon

    2016-01-01

    A nerve block is an effective tool for diagnostic and therapeutic methods. If a diagnostic nerve block is successful for pain relief and the subsequent therapeutic nerve block is effective for only a limited duration, the next step that should be considered is a nerve ablation or modulation. The nerve ablation causes iatrogenic neural degeneration aiming only for sensory or sympathetic denervation without motor deficits. Nerve ablation produces the interruption of axonal continuity, degeneration of nerve fibers distal to the lesion (Wallerian degeneration), and the eventual death of axotomized neurons. The nerve ablation methods currently available for resection/removal of innervation are performed by either chemical or thermal ablation. Meanwhile, the nerve modulation method for interruption of innervation is performed using an electromagnetic field of pulsed radiofrequency. According to Sunderland's classification, it is first and foremost suggested that current neural ablations produce third degree peripheral nerve injury (PNI) to the myelin, axon, and endoneurium without any disruption of the fascicular arrangement, perineurium, and epineurium. The merit of Sunderland's third degree PNI is to produce a reversible injury. However, its shortcoming is the recurrence of pain and the necessity of repeated ablative procedures. The molecular mechanisms related to axonal regeneration after injury include cross-talk between axons and glial cells, neurotrophic factors, extracellular matrix molecules, and their receptors. It is essential to establish a safe, long-standing denervation method without any complications in future practices based on the mechanisms of nerve degeneration as well as following regeneration. PMID:26839664

  16. An experimental study of simultaneous ablation with dual probes in radiofrequency thermal ablation

    Jang, Il Soo; Rhim, Hyun Chul; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Kim, Yong Soo; Kim, Young Sun; Heo, Jeong Nam [Hanyang University College of Medicine, Seoul (Korea, Republic of)

    2003-02-01

    To determine the differences between sequential ablation with a single probe and simultaneous ablation with dual probes. Using two 14-gauge expandable probes (nine internal prongs with 4-cm deployment), radiofrequency was applied sequentially (n=8) or simultaneously (n=8) to ten ex-vivo cow livers. Before starting ablation, two RF probes with an inter-probe space of 2 cm (n=8) or 3 cm (n=8) were inserted. In the sequential group, switching the connecting cable to an RF generator permitted ablation with the second probe just after ablation with the first probe had finished. In the simultaneous group, single ablation was performed only after connecting the shafts of both RF probes using a connection device. Each ablation lasted 7 minutes at a target temperature of 105-110 .deg. C. The size and shape of the ablated area, and total ablation time were then compared between the two groups. With 2-cm spacing, the group, mean length and overlapping width of ablated lesions were, respectively, 5.20 and 5.05 cm in the sequential group (n=4), and 5.81 and 5.65 cm in the simultaneous group (n=4). With 3-cm spacing, the corresponding figures were 4.99 and 5.60 cm in the sequential group (n=4), and 6.04 and 6.78 cm in the simultaneous group (n=4). With 2-cm spacing, the mean depth of the proximal waist was 0.58 cm in the sequential (group and 0.28 cm in the simultaneous group, while with 3-cm spacing, the corresponding figures were 1.65 and 1.48 cm. In neither group was there a distal waist. Mean total ablation time was 23.4 minutes in the sequential group and 14 minutes in the simultaneous group. In terms of ablation size and ablation time, simultaneous radiofrequency ablation with dual probes is superior to sequential ablation with a single probe. A simultaneous approach will enable an operator to overcome difficulty in probe repositioning during overlapping ablation, resulting in complete ablation with a successful safety margin.

  17. Thermal protection system ablation sensor

    Gorbunov, Sergey (Inventor); Martinez, Edward R. (Inventor); Scott, James B. (Inventor); Oishi, Tomomi (Inventor); Fu, Johnny (Inventor); Mach, Joseph G. (Inventor); Santos, Jose B. (Inventor)

    2011-01-01

    An isotherm sensor tracks space vehicle temperatures by a thermal protection system (TPS) material during vehicle re-entry as a function of time, and surface recession through calibration, calculation, analysis and exposed surface modeling. Sensor design includes: two resistive conductors, wound around a tube, with a first end of each conductor connected to a constant current source, and second ends electrically insulated from each other by a selected material that becomes an electrically conductive char at higher temperatures to thereby complete an electrical circuit. The sensor conductors become shorter as ablation proceeds and reduced resistance in the completed electrical circuit (proportional to conductor length) is continually monitored, using measured end-to-end voltage change or current in the circuit. Thermocouple and/or piezoelectric measurements provide consistency checks on local temperatures.

  18. Laser induced ablation studies from gold target

    Laser produced gold plasmas show an enhanced mass ablation rate and ablation pressure as compared to theoretical prediction. This is attributed to radiation effect. Experimental results indicate an increase in the C-J point density and an agreement with self-regulating ablation scaling. Using 1.06 μm laser radiation on 12.5 μm thick planar gold targets, at an absorbed laser intensity IA ≤ 2 x 1013 W/cm2, the experimental results are presented. (Author)

  19. Catheter ablation of inappropriate sinus tachycardia.

    Gianni, Carola; Di Biase, Luigi; Mohanty, Sanghamitra; Gökoğlan, Yalçın; Güneş, Mahmut F; Horton, Rodney; Hranitzky, Patrick M; Burkhardt, J David; Natale, Andrea

    2016-06-01

    Catheter ablation for inappropriate sinus tachycardia (IST) is recommended for patients symptomatic for palpitations and refractory to other treatments. The current approach consists in sinus node modification (SNM), achieved by ablation of the cranial part of the sinus node to eliminate faster sinus rates while trying to preserve chronotropic competence. This approach has a limited efficacy, with a very modest long-term clinical success. To overcome this, proper patient selection is crucial and an epicardial approach should always be considered. This brief review will discuss the current role and limitations of catheter ablation in the management of patients with IST. PMID:26310299

  20. Atrioventricular Junction Ablation for Atrial Fibrillation.

    Patel, Dilesh; Daoud, Emile G

    2016-04-01

    Atrioventricular junction (AVJ) ablation is an effective therapy in patients with symptomatic atrial fibrillation who are intolerant to or unsuccessfully managed with rhythm control or medical rate control strategies. A drawback is that the procedure mandates a pacing system. Overall, the safety and efficacy of AVJ ablation is high with a majority of the patients reporting significant improvement in symptoms and quality-of-life measures. Risk of sudden cardiac death after device implantation is low, especially with an appropriate postprocedure pacing rate. Mortality benefit with AVJ ablation has been shown in patients with heart failure and cardiac resynchronization therapy devices. PMID:26968669

  1. How I do it: Radiofrequency ablation

    Over the past decade, image-guided tumor ablation using thermal energy has emerged as a promising technique for treating focal, primary or secondary, nonoperable tumors. Radiofrequency ablation (RFA) is minimally invasive and requires less resources, time, and recovery period and is, moreover, relatively inexpensive. RFA has been used to treat tumors located in the liver, lung, bone, kidneys, brain, thyroid, breast, and pancreas. This article will describe how to choose an appropriate case; precisely place the needle into the tumor; the precautions to be taken before, during, and after the procedure; probable complications; and the follow-up of patients undergoing ablation

  2. Tumor Ablation: Common Modalities and General Practices

    Knavel, Erica M.; Brace, Christopher L.

    2013-01-01

    Tumor ablation is a minimally invasive technique that is commonly used in the treatment of tumors of the liver, kidney, bone, and lung. During tumor ablation, thermal energy is used to heat or cool tissue to cytotoxic levels (less than −40°C or more than 60°C). An additional technique is being developed that targets the permeability of the cell membrane and is ostensibly nonthermal. Within the classification of tumor ablation, there are several modalities used worldwide: radiofrequency, micro...

  3. The Atrial Fibrillation Ablation Pilot Study

    Arbelo, Elena; Brugada, Josep; Hindricks, Gerhard;

    2014-01-01

    AIMS: The Atrial Fibrillation Ablation Pilot Study is a prospective registry designed to describe the clinical epidemiology of patients undergoing an atrial fibrillation (AFib) ablation, and the diagnostic/therapeutic processes applied across Europe. The aims of the 1-year follow-up were to analyse...... left atrial tachycardia, and 4 patients died (1 haemorrhagic stroke, 1 ventricular fibrillation in a patient with ischaemic heart disease, 1 cancer, and 1 of unknown cause). CONCLUSION: The AFib Ablation Pilot Study provided crucial information on the epidemiology, management, and outcomes of catheter...

  4. Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

  5. Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

    Baladi, Arash [Materials Engineering Department, Tarbiat Modares University, Jalal Al Ahmad, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Sarraf Mamoory, Rasoul, E-mail: rsarrafm@modares.ac.ir [Materials Engineering Department, Tarbiat Modares University, Jalal Al Ahmad, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2010-10-01

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

  6. Typical flutter ablation as an adjunct to catheter ablation of atrial fibrillation

    Dipen Shah

    2008-01-01

    Typical atrial flutter and atrial fibrillation are frequently observed to coexist(1) .  In the current context of interventional electrophysiology, curative or at least definitive ablation is available for both arrhythmias. Despite their coexistence, it is not clear whether typical flutter ablation is necessary in all patients undergoing catheter ablation of atrial fibrillation. The following review explores the pathophysiology of both arrhythmias, their interrelationships and the availa...

  7. Typical flutter ablation as an adjunct to catheter ablation of atrial fibrillation

    Dipen Shah

    2008-12-01

    Full Text Available Typical atrial flutter and atrial fibrillation are frequently observed to coexist(1 .  In the current context of interventional electrophysiology, curative or at least definitive ablation is available for both arrhythmias. Despite their coexistence, it is not clear whether typical flutter ablation is necessary in all patients undergoing catheter ablation of atrial fibrillation. The following review explores the pathophysiology of both arrhythmias, their interrelationships and the available data pertaining to this theme.

  8. Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation): A Review

    Salvatore Paiella; Roberto Salvia; Marco Ramera; Roberto Girelli; Isabella Frigerio; Alessandro Giardino; Valentina Allegrini; Claudio Bassi

    2016-01-01

    Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC) accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA) and Irreversible Electroporation (IRE) are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on ...

  9. Epitaxial growth by monolayer restricted galvanic displacement

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  10. Making work safe for displaced women

    Dale Buscher

    2012-12-01

    Full Text Available Displaced women need opportunities to make a living for themselves and their families but these opportunities should not increase their vulnerability. Understanding risk factors and protection strategies allows practitioners to ensure appropriate programme design and implementation.

  11. A flexible sensor measuring displacement and bending

    Nishijima, Takashi; Yamamoto, Akio; Higuchi, Toshiro

    2009-04-01

    This paper proposes a new sensor that is capable of measuring both linear displacement and bending. The sensor is designed to be used with an electrostatic film motor that features mechanical flexibility, but can also be used as an independent sensor. The sensor employs three-phase electrodes both in sliding and stationary parts and estimates displacement and bending from the change of the capacitance between the electrodes. The paper describes an equivalent capacitance-network model for the sensor. Based on the model, sensing principles for both displacement and bending are presented and analyzed. The analyses are experimentally verified using a prototype sensor. The experimental results show that the prototype sensor could measure both displacement and bending with little interference between them.

  12. Precision optical displacement measurements using biphotons

    Lyons, Kevin; Pang, Shengshi; Kwiat, Paul G.; Jordan, Andrew N

    2016-01-01

    We propose and examine the use of biphoton pairs, such as those created in parametric down conversion or four-wave mixing, to enhance the precision and the resolution of measuring optical displacements by position-sensitive detection. We show that the precision of measuring a small optical beam displacement with this method can be significantly enhanced by the correlation between the two photons, given the same optical mode. The improvement is largest if the correlations between the photons a...

  13. Atrial Tachycardias Occurring After Atrial Fibrillation Ablation: Strategies for Mapping and Ablation

    Stavros Mountantonakis, MD

    2010-10-01

    Full Text Available The occurrence of left atrial tachycardias (AT after catheter ablation for atrial fibrillation (AF is common, especially after more extensive ablation of persistent AF. These AT are invariably symptomatic and often do not respond to medical therapy. The initial strategy involves ventricular rate control, cardioversion, and observation as some tachycardias may resolve with time. For persistent ATs, effective management frequently requires catheter intervention. Careful characterization of the tachycardia mechanism is essential in designing an effective ablation strategy that would also avoid further creation of pro-arrhythmic substrate. With this review, we summarize the incidence, mechanism, diagnosis and treatment of ATs occurring after AF ablation.

  14. Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency

    Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2015-02-01

    The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3/J when the laser fluence was set at 6.51 J/cm2. For enamel, the maximum ablation efficiency was 0.009 mm3/J at a fluence of 7.59 J/cm2. Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value.

  15. Effect of ambient air pressure on debris redeposition during laser ablation of glass

    The effect of ambient air pressure on the redeposition of debris, ablated from the zinc borosilicate glass target using 6 ns, 266 nm laser pulses, has been studied for incident fluences of 3-18 J/cm2. Measurements were carried out in air at pressures ranging from 10-750 Torr. Scanning electron microscopy and optical microscope observations of the target surface were made to analyze the morphology of the redeposited debris. It was found that for higher values of the laser fluence and ambient pressure, the target surface is extremely rough, with large pieces of molten glass and debris fragments deposited near and around the ablation site. The profile of the redeposited debris also shows signs of a strong shock-wave-cleaning effect and possibly a Rayleigh-Taylor instability at higher pressures. Contrary to this, under low-pressure environment the surface of the redeposited debris is cleaner and smoother, with minimal damage around the ablated crater. The measured radius of the debris field was found to be proportional to the inverse cube root of the ambient pressure, consistent with the stagnation distance of the expansion plume when energy balance with the displaced air is considered. In addition to this, the mass of the redeposited debris was estimated from the measured optical thickness of the film and compared to the ablated mass. In the range below 100 Torr, both the mass of the redeposited debris and the percentage of the ablated mass which was redeposited were found to increase with the increasing fluence and the ambient air pressure

  16. Simple spherical ablative-implosion model

    A simple model of the ablative implosion of a high-aspect-ratio (shell radius to shell thickness ratio) spherical shell is described. The model is similar in spirit to Rosenbluth's snowplow model. The scaling of the implosion time was determined in terms of the ablation pressure and the shell parameters such as diameter, wall thickness, and shell density, and compared these to complete hydrodynamic code calculations. The energy transfer efficiency from ablation pressure to shell implosion kinetic energy was examined and found to be very efficient. It may be possible to attach a simple heat-transport calculation to our implosion model to describe the laser-driven ablation-implosion process. The model may be useful for determining other energy driven (e.g., ion beam) implosion scaling

  17. Laser-Induced Ablative Amorphisation of Montmorillonite

    Duchek, P.; Urbanová, Markéta; Pokorná, Dana; Kupčík, Jaroslav; Šubrt, Jan; Pola, Josef

    2012-01-01

    Roč. 358, č. 23 (2012), s. 3382-3387. ISSN 0022-3093 Institutional support: RVO:67985858 ; RVO:61388980 Keywords : laser ablation * montmorillonite * amorphization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.597, year: 2012

  18. Laser ablation in analytical chemistry - A review

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  19. Optical Effects on Laser Ablated Polymer Surfaces

    Prabhu, R. D.; Govinthasamy, R.; Murthy, N. S.

    2006-03-01

    Laser ablation of poly (ethylene terephthalate) and polyimide films were investigated using Excimer-UV laser. SEM analyses indicate the presence of rings for a wide range of ablation parameters (fluence, frequency and number of pulses). It is proposed that the particles present in the plasma plume could cause the incident laser light to diffract, similar to the optical effects observed in the femtosecond laser ablation of solids. The polymer surface provides a perfect medium to register the optical signatures as seen in the SEM images. The fringe-spacings observed in the images are compared with the theoretical diffraction patterns and the height of the plasma particles above the surface is estimated using an optimization scheme. The results of the analysis are consistent with experimentally observed dynamics of the plasma plume. It is proposed that such optical effects could be a routine feature in the laser ablation of polymers. The significance of such artifacts for lithography is discussed.

  20. Thermal Ablation Modeling for Silicate Materials

    Chen, Yih-Kanq

    2016-01-01

    A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  1. Ablative Ceramic Foam Based TPS Project

    National Aeronautics and Space Administration — A novel composite material ablative TPS for planetary vehicles that can survive a dual heating exposure is proposed. NextGen's TPS concept is a bi-layer functional...

  2. Diagnostics of laser ablated plasma plumes

    Amoruso, S.; Toftmann, B.; Schou, Jørgen;

    2004-01-01

    The effect of an ambient gas on the expansion dynamics of laser ablated plasmas has been studied for two systems by exploiting different diagnostic techniques. First, the dynamics of a MgB2 laser produced plasma plume in an Ar atmosphere has been investigated by space-and time-resolved optical...... laser ablated plasma plume propagation in a background gas. (C) 2003 Elsevier B.V All rights reserved....

  3. Phased RF ablation: results and concerns

    Alexandra Kiss, MD, PhD; G�bor S�ndorfi, MD; Edina Nagy-Bal�, MD, PhD; Mihran Martirosyan, MD; Zoltan Csanadi, MD, PhD

    2015-01-01

    reatment of atrial fibrillation (AF) with catheter ablation has proven to be a safe and effective treatment modality which is offered to an increasing number of patients in many centers. Pulmonary vein isolation (PVI) is an established cornerstone of AF ablation strategies. Athough the isolation of the pulmonary veins (PVs) with irrigated focal radiofrequency (RF) catheters using a point-by-point method is considered as the gold standard, it can be challenging to create contiguous lesions, ti...

  4. Photogrammetric recession measurements of an ablating surface

    Schairer, Edward T. (Inventor); Heineck, James T. (Inventor)

    2012-01-01

    An instrument and method for measuring the time history of recession of an ablating surface of a test article during testing in a high enthalpy thermal test facility, such as an arcjet. The method advances prior art by providing time-history data over the full ablating surface without targets and without any modifications to the test article. The method is non-intrusive, simple to implement, requires no external light source, and does not interfere with normal operations of the arcjet facility.

  5. Hydrodynamic modeling of ns-laser ablation

    David Autrique; Vasilios Alexiades; Harihar Khanal

    2013-01-01

    Laser ablation is a versatile and widespread technique, applied in an increasing number of medical, industrial and analytical applications. A hydrodynamic multiphase model describing nanosecond-laser ablation (ns-LA) is outlined. The model accounts for target heating and mass removal mechanisms as well as plume expansion and plasma formation. A copper target is placed in an ambient environment consisting of helium and irradiated by a nanosecond-laser pulse. The effect of variable laser ...

  6. Simple ablative implosion model: shell dynamics

    A simple model, derived from Newton's Second Law, for the ablative implosion of a thin spherical shell is presented. The scaling dependence of the implosion time, shell velocity, and mass loss on shell dimensions and the critical physical parameter, the ablation pressure, is derived. Finally, the model is used to examine implosion energy efficiency and to describe an interesting application, wall-recoil heating of a contained fuel gas

  7. Retained Foreign Body After Laser Ablation

    Ren, Shiyan; Liu, Peng; Wang, Wei; Yang, Yuguan

    2012-01-01

    Laser ablation for varicose veins is a common practice, and postoperative complications may happen. A retained foreign body could be left accidently in the treated leg. It is rarely reported in literature. We herein describe two cases of retained foreign body during the laser ablation for varicose veins. One patient with varicose veins received laser therapy 5 years earlier, and had experienced discomfort and pain. After investigation, an overlooked sheath fragment was removed surgically from...

  8. Displaced and non-displaced Colombian children's evaluations of moral transgressions, retaliation, and reconciliation

    Ardila-Rey, Alicia; Killen, Melanie; Brenick, Alaina

    2009-01-01

    In order to assess the effects of displacement and exposure to violence on children's moral reasoning, Colombian children exposed to minimal violence (non-displaced or low-risk) (N = 99) and to extreme violence (displaced or high-risk) (N = 94), evenly divided by gender, at 6-, 9-, and 12 - years of age, were interviewed regarding their evaluation of peer-oriented moral transgressions (hitting and not sharing toys). The vast majority of children evaluated moral transgressions as wrong. Group ...

  9. Basic ablation phenomena during laser thrombolysis

    Sathyam, Ujwal S.; Shearin, Alan; Prahl, Scott A.

    1997-05-01

    This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

  10. Laser Ablation for Small Hepatocellular Carcinoma

    Pacella, Claudio Maurizio; Francica, Giampiero; Di Costanzo, Giovanni Giuseppe

    2011-01-01

    Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600 μm inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment. PMID:22191028

  11. Percutaneous Microwave Ablation of Renal Angiomyolipomas

    PurposeTo evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML).Materials and MethodsFrom January 2011 to April 2014, seven patients (5 females and 2 males; mean age 51.4) with 11 renal AMLs (9 sporadic type and 2 tuberous sclerosis associated) with a mean size of 3.4 ± 0.7 cm (range 2.4–4.9 cm) were treated with high-powered, gas-cooled percutaneous MW ablation under US guidance. Tumoral diameter, volume, and CT/MR enhancement were measured on pre-treatment, immediate post-ablation, and delayed post-ablation imaging. Clinical symptoms and creatinine were assessed on follow-up visits.ResultsAll ablations were technically successful and no major complications were encountered. Mean ablation parameters were ablation power of 65 W (range 60–70 W), using 456 mL of hydrodissection fluid per patient, over 4.7 min (range 3–8 min). Immediate post-ablation imaging demonstrated mean tumor diameter and volume decreases of 1.8 % (3.4–3.3 cm) and 1.7 % (27.5–26.3 cm3), respectively. Delayed imaging follow-up obtained at a mean interval of 23.1 months (median 17.6; range 9–47) demonstrated mean tumor diameter and volume decreases of 29 % (3.4–2.4 cm) and 47 % (27.5–12.1 cm3), respectively. Tumoral enhancement decreased on immediate post-procedure and delayed imaging by CT/MR parameters, indicating decreased tumor vascularity. No patients required additional intervention and no patients experienced spontaneous bleeding post-ablation.ConclusionOur early experience with high-powered, gas-cooled percutaneous MW ablation demonstrates it to be a safe and effective modality to devascularize and decrease the size of renal AMLs

  12. Percutaneous Microwave Ablation of Renal Angiomyolipomas

    Cristescu, Mircea, E-mail: mcristescu@uwhealth.org [University of Wisconsin, Department of Radiology (United States); Abel, E. Jason, E-mail: abel@urology.wisc.edu [University of Wisconsin, Department of Urology (United States); Wells, Shane, E-mail: swells@uwhealth.org; Ziemlewicz, Timothy J., E-mail: tziemlewicz@uwhealth.org [University of Wisconsin, Department of Radiology (United States); Hedican, Sean P., E-mail: hedican@surgery.wisc.edu [University of Wisconsin, Department of Urology (United States); Lubner, Megan G., E-mail: mlubner@uwhealth.org; Hinshaw, J. Louis, E-mail: jhinshaw@uwhealth.org; Brace, Christopher L., E-mail: cbrace@uwhealth.org; Lee, Fred T., E-mail: flee@uwhealth.org [University of Wisconsin, Department of Radiology (United States)

    2016-03-15

    PurposeTo evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML).Materials and MethodsFrom January 2011 to April 2014, seven patients (5 females and 2 males; mean age 51.4) with 11 renal AMLs (9 sporadic type and 2 tuberous sclerosis associated) with a mean size of 3.4 ± 0.7 cm (range 2.4–4.9 cm) were treated with high-powered, gas-cooled percutaneous MW ablation under US guidance. Tumoral diameter, volume, and CT/MR enhancement were measured on pre-treatment, immediate post-ablation, and delayed post-ablation imaging. Clinical symptoms and creatinine were assessed on follow-up visits.ResultsAll ablations were technically successful and no major complications were encountered. Mean ablation parameters were ablation power of 65 W (range 60–70 W), using 456 mL of hydrodissection fluid per patient, over 4.7 min (range 3–8 min). Immediate post-ablation imaging demonstrated mean tumor diameter and volume decreases of 1.8 % (3.4–3.3 cm) and 1.7 % (27.5–26.3 cm{sup 3}), respectively. Delayed imaging follow-up obtained at a mean interval of 23.1 months (median 17.6; range 9–47) demonstrated mean tumor diameter and volume decreases of 29 % (3.4–2.4 cm) and 47 % (27.5–12.1 cm{sup 3}), respectively. Tumoral enhancement decreased on immediate post-procedure and delayed imaging by CT/MR parameters, indicating decreased tumor vascularity. No patients required additional intervention and no patients experienced spontaneous bleeding post-ablation.ConclusionOur early experience with high-powered, gas-cooled percutaneous MW ablation demonstrates it to be a safe and effective modality to devascularize and decrease the size of renal AMLs.

  13. Dust ablation in Pluto's atmosphere

    Horanyi, Mihaly; Poppe, Andrew; Sternovsky, Zoltan

    2016-04-01

    Based on measurements by dust detectors onboard the Pioneer 10/11 and New Horizons spacecraft the total production rate of dust particles born in the Edgeworth Kuiper Belt (EKB) has been be estimated to be on the order of 5 ṡ 103 kg/s in the approximate size range of 1 - 10 μm. Dust particles are produced by collisions between EKB objects and their bombardment by both interplanetary and interstellar dust particles. Dust particles of EKB origin, in general, migrate towards the Sun due to Poynting-Robertson drag but their distributions are further sculpted by mean-motion resonances as they first approach the orbit of Neptune and later the other planets, as well as mutual collisions. Subsequently, Jupiter will eject the vast majority of them before they reach the inner solar system. The expected mass influx into Pluto atmosphere is on the order of 200 kg/day, and the arrival speed of the incoming particles is on the order of 3 - 4 km/s. We have followed the ablation history as function of speed and size of dust particles in Pluto's atmosphere, and found that volatile rich particles can fully sublimate due to drag heating and deposit their mass in narrow layers. This deposition might promote the formation of the haze layers observed by the New Horizons spacecraft. This talk will explore the constraints on the composition of the dust particles by comparing the altitude of the deposition layers to the observed haze layers.

  14. Lip Reconstruction after Tumor Ablation

    Ebrahimi, Ali; Kalantar Motamedi, Mohammad Hossein; Ebrahimi, Azin; Kazemi, Mohammad; Shams, Amin; Hashemzadeh, Haleh

    2016-01-01

    Approximately 25% of all oral cavity carcinomas involve the lips, and the primary management of these lesions is complete surgical resection. Loss of tissue in the lips after resection is treated with a variety of techniques, depending on the extension and location of the defect. Here we review highly accepted techniques of lip reconstruction and some of new trials with significant clinical results. Reconstruction choice is primarily depend to size of the defect, localization of defect, elasticity of tissues. But patient’s age, comorbidities, and motivation are also important. According to the defect location and size, different reconstruction methods can be used. For defects involved less than 30% of lips, primary closures are sufficient. In defects with 35–70% lip involvement, the Karapandzic, Abbe, Estlander, McGregor or Gillies’ fan flaps or their modifications can be used. When lip remaining tissues are insufficient, cheek tissue can be used in Webster and Bernard advancement flaps and their various modifications. Deltopectoral or radial forearm free flaps can be options for large defects of the lip extending to the Jaws. To achieve best functional and esthetic results, surgeons should be able to choose most appropriate reconstruction method. Considering defects’ size and location, patients’ expects and surgeon’s ability and knowledge, a variety of flaps are presented in order to reconstruct defects resulted from tumor ablation. It’s necessary for surgeons to trace the recent innovations in lip reconstruction to offer best choices to patients. PMID:27308236

  15. Fractional ablative erbium YAG laser

    Taudorf, Elisabeth H; Haak, Christina S; Erlendsson, Andrés M;

    2014-01-01

    BACKGROUND AND OBJECTIVES: Treatment of a variety of skin disorders with ablative fractional lasers (AFXL) is driving the development of portable AFXLs. This study measures micropore dimensions produced by a small 2,940 nm AFXL using a variety of stacked pulses, and determines a model correlating...... laser parameters with tissue effects. MATERIALS AND METHODS: Ex vivo pig skin was exposed to a miniaturized 2,940 nm AFXL, spot size 225 µm, density 5%, power levels 1.15-2.22 W, pulse durations 50-225 microseconds, pulse repetition rates 100-500 Hz, and 2, 20, or 50 stacked pulses, resulting in pulse...... 190 to 347 µm. CONCLUSIONS: Pulse stacking with a small, low power 2,940 nm AFXL created reproducible shallow to deep micropores, and influenced micropore configuration. Mathematical modeling established relations between laser settings and micropore dimensions, which assists in choosing laser...

  16. Effect of ablatant composition on the ablation of a fuelling pellet

    The single species neutral-shielding model for the ablation of a hydrogenic pellet is extended by considering the ablatant as a mixture of four species: molecular and atomic hydrogen, protons and electrons. Compared with the results of the frozen flow, (i.e. the single species molecular hydrogen gas model), results of the analysis showed that the presence of dissociation and ionization effects caused a marked difference of the ablatant state. The attenuations of the incoming electron energy and energy flux, however, are very much similar irrespective of whether the ablated flow is in a frozen or an equilibrium state. The scaling law of the pellet ablation rate with respect to the plasma state of Te, ne and the pellet radius remains the same; the ablation rate is reduced by approximately 15%. To examine the possible existence of a spherical shell around the pellet where most of the incoming electron energy is absorbed, acodmparison is made between the local electron collisional mean free path and the electron Larmor radius. A critical field at the ionization radius is evaluated. An effective spherical energyabsorbing region exists when the local field strength is below the critical value. For a plasma state of low Te and ne, (where the ablatant is hardly ionized), and for one near the thermonuclear condition (where a highly dense ablatant exists near the pellet), the effective energy absorption region is nearly spherical. 20 refs. (author)

  17. Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation

    Christensen, Bo Toftmann; Doggett, B.; Budtz-Jørgensen, C.;

    2013-01-01

    The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at ~2 J cm-2 has been studied using angle-resolved Langmuir ion probe and thin film deposition techniques. For the same laser fluence, the time-of-flight ion signals from femtosecond and nanosecond laser...

  18. Atomic displacements in bcc dilute alloys

    Hitesh Sharma; S Prakash

    2007-04-01

    We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method. Wills and Harrison interatomic potential is used to calculate the atomic force constants, the dynamical matrix and the impurity-induced forces. We have thoroughly investigated the atomic displacements using impurities from 3d, 4d and 5d series in the same host metal and the same impurity in different hosts. We have observed a systematic pattern in the atomic displacements for Cr-, Fe-, Nb-, Mo-, Ta- and W-based dilute alloys. The atomic displacements are found to increase with increase in the number of d electrons for all alloys considered except for V dilute alloys. The 3d impurities are found to be more easily dissolved in the 3d host metals than 4d or 5d TMs whereas 4d and 5d impurities show more solubility in 4d and 5d TMs. In general, the relaxation energy calculation suggests that impurities may be easily solvable in 5d TM hosts when compared to 3d or 4d TMs.

  19. Quantification of the vocal folds’ dynamic displacements

    del Socorro Hernández-Montes, María; Muñoz, Silvino; De La Torre, Manuel; Flores, Mauricio; Pérez, Carlos; Mendoza-Santoyo, Fernando

    2016-05-01

    Fast dynamic data acquisition techniques are required to investigate the motional behavior of the vocal folds (VFs) when they are subjected to a steady air-flow through the trachea. High-speed digital holographic interferometry (DHI) is a non-invasive full-field-of-view technique that has proved its usefulness to study rapid and non-repetitive object movements. Hence it is an ideal technique used here to measure VF displacements and vibration patterns at 2000 fps. Analyses from a set of 200 displacement images showed that VFs’ vibration cycles are established along their width (y) and length (x). Furthermore, the maximum deformation for the right and left VFs’ area may be quantified from these images, which in itself represents an important result in the characterization of this structure. At a controlled air pressure, VF displacements fall within the range ~100-1740 nm, with a calculated precision and accuracy that yields a variation coefficient of 1.91%. High-speed acquisition of full-field images of VFs and their displacement quantification are on their own significant data in the study of their functional and physiological behavior since voice quality and production depend on how they vibrate, i.e. their displacement amplitude and frequency. Additionally, the use of high speed DHI avoids prolonged examinations and represents a significant scientific and technological alternative contribution in advancing the knowledge and working mechanisms of these tissues.

  20. Radiofrequency thermal ablation of malignant hepatic tumors: post-ablation syndrome

    To evaluate post-ablation syndrome after radiofrequency thermal ablation of malignant hepatic tumors. Forty-two patients with primary (n=3D29) or secondary (n=3D13) hepatic tumors underwent radiofrequency thermal ablation. A total of 65 nodules ranging in size from 1.1 to 5.0 (mean, 3.1) cm were treated percutaneously using a 50W RF generator with 15G expandable needle electrodes. We retrospectively evaluated the spectrum of post-ablation syndrome including pain, fever (≥3D 38 deg C), nausea, vomiting, right shoulder pain, and chest discomfort according to frequency, intensity and duration, and the findings were correlated with tumor location and number of ablations. We also evaluated changes in pre-/post-ablation serum aminotransferase (ALT/AST) and prothrombin time, and correlated these findings with the number of ablations. Post-ablation syndrome was noted in 29 of 42 patients (69.0%), and most symptoms improved with conservative treatment. The most important of these were abdominal plan (n=3D20, 47.6%), fever (n=3D8, 19.0%), and nausea (n=3D7, 16.7%), and four of 42 (9.5%) patients complained of severe pain. The abdominal pain lasted from 3 hours to 5.5 days (mean; 20.4 hours), the fever from 6 hours to 5 days (mean; 63.0 hours). And the nausea from 1 hours to 4 days (mean; 21.0 hours). Other symptoms were right shoulder pain (n=3D6, 14.3%), chest discomfort (n=3D3, 7.1%), and headache (n=3D3, 7.1%). Seventeen of 20 patients (85%) with abdominal pain had subcapsular tumor of the liver. There was significant correlation between pain, location of the tumor, and a number of ablations. After ablation, ALT/AST was elevated more than two-fold in 52.6%/73.7% of patients, respectively but there was no significant correlation with the number of ablation. Post-ablation syndrome is a frequent and tolerable post-procedural process after radiofrequency thermal ablation. The spectrum of this syndrome provides a useful guideline for the post-ablation management. (author)

  1. Radiofrequency thermal ablation of malignant hepatic tumors: post-ablation syndrome

    Choi, Jung Bin; Rhim, Hyunchul; Kim, Yongsoo; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Lee, Seung Ro [College of Medicine, Hanyang University, Seoul (Korea, Republic of)

    2000-07-01

    To evaluate post-ablation syndrome after radiofrequency thermal ablation of malignant hepatic tumors. Forty-two patients with primary (n=3D29) or secondary (n=3D13) hepatic tumors underwent radiofrequency thermal ablation. A total of 65 nodules ranging in size from 1.1 to 5.0 (mean, 3.1) cm were treated percutaneously using a 50W RF generator with 15G expandable needle electrodes. We retrospectively evaluated the spectrum of post-ablation syndrome including pain, fever ({>=}3D 38 deg C), nausea, vomiting, right shoulder pain, and chest discomfort according to frequency, intensity and duration, and the findings were correlated with tumor location and number of ablations. We also evaluated changes in pre-/post-ablation serum aminotransferase (ALT/AST) and prothrombin time, and correlated these findings with the number of ablations. Post-ablation syndrome was noted in 29 of 42 patients (69.0%), and most symptoms improved with conservative treatment. The most important of these were abdominal plan (n=3D20, 47.6%), fever (n=3D8, 19.0%), and nausea (n=3D7, 16.7%), and four of 42 (9.5%) patients complained of severe pain. The abdominal pain lasted from 3 hours to 5.5 days (mean; 20.4 hours), the fever from 6 hours to 5 days (mean; 63.0 hours). And the nausea from 1 hours to 4 days (mean; 21.0 hours). Other symptoms were right shoulder pain (n=3D6, 14.3%), chest discomfort (n=3D3, 7.1%), and headache (n=3D3, 7.1%). Seventeen of 20 patients (85%) with abdominal pain had subcapsular tumor of the liver. There was significant correlation between pain, location of the tumor, and a number of ablations. After ablation, ALT/AST was elevated more than two-fold in 52.6%/73.7% of patients, respectively but there was no significant correlation with the number of ablation. Post-ablation syndrome is a frequent and tolerable post-procedural process after radiofrequency thermal ablation. The spectrum of this syndrome provides a useful guideline for the post-ablation management. (author)

  2. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  3. Ultra-short laser ablation of dielectrics: Theoretical analysis of threshold damage fluence and ablation depth

    A coupled theoretical model based on Fokker-Planck equation for ultra-short laser ablation of dielectrics is proposed. Multiphoton ionization and avalanche ionization are considered as the sources during the generation of free electrons. The impact of the electron distribution in thermodynamic nonequilibrium on relaxation time is taken into account. The calculation formula of ablation depth is deduced based on the law of energy conservation. Numerical calculations are performed for the femtosecond laser ablation of fused silica at 526 and 1053 nm. It shows that the threshold damage fluences and ablation depths resulted from the coupled model are in good agreement with the experimental results; while the damage thresholds resulted from the approximate model significantly differ from the experimental results for lasers of long pulse width. It is concluded that the coupled model can better describe the micro-process of ultra-short laser ablation of dielectrics.

  4. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  5. MR Guided RF Ablation and Thermometery

    Sara Eskandari

    2009-01-01

    Full Text Available "nIntroduction: Liver metastasis is detected in more than one million people in each year. Only 10% of them are eligible for surgery. Radiofrequency ablation is the most popular local ablation technique for the management of the other 90% of the metastases. Complete ablation of the lesion with a safe margin is the goal of such a local ablative method. There is no routine available technique for monitoring the treatment process. MRI is the only method which can monitor tissue ablation in real time however interaction of radiofrequency energy by MRI acquisition makes it impossible for clinical use. "nMaterials and Methods: In our in-vitro study, the effect of bipolar needles were evaluated on the signal intensity of theliver parenchyma. This evaluation was repeated 15 times. A calibration curve was also calculated from the in-vitro measurement of tissue temperature with an interstitial NTC sensor with dedicated data collecting software written by our team. Finally the correlation between temperature and signal intensity was prepared and during the RF ablation, the temperature map could be created in an almost real time manner. "nResults: Our results show an exponential calibration curve for sensors and a linear reduction of the signal intensities during the RF procedure. "nConclusion: We introduce a method for calibration of the MRI signal intensity with tissue temperature between alternative RF pulses. This method brings MR monitoring as the practical method in clinical use. By this innovative technique it is possible for all the hospitals and clinics to use their routine MR scanner for monitoring this ablative technique without any additional hardware.  

  6. Photoacoustic characterization of radiofrequency ablation lesions

    Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

    2012-02-01

    Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

  7. Laser ablation of hepatocellular carcinoma-A review

    2008-01-01

    A wide range of local thermal ablative therapies have been developed in the treatment of non resectable hepatocellular carcinoma (HCC) in the last decade. Laser ablation (LA) and radiofrequency ablation (RFA) are the two most widely used of these. This article provides an up to date overview of the role of laser ablation in the local treatment of HCC. General principles, technique, image guidance and patient selection are discussed. A review of published data on treatment efficacy, long term outcome and complication rates of laser ablation is included and comparison with RFA made. The role of laser ablation in combination with transcatheter arterial chemoembolisation is also discussed.

  8. Forced displacement and women's security in Colombia.

    Meertens, Donny

    2010-04-01

    In the protracted Colombian conflict, assistance to internally displaced persons has developed in the context of contradictory political processes. The Colombian government's launching of a transitional justice process in the midst of armed conflict has generated a complex situation displaying both conflict and post-conflict characteristics. The progressive Constitutional Court rulings on internal displacement, in particular the gender-sensitive Auto 092, constitute an attempt to bring together humanitarian interventions and transitional justice measures in a rights-based framework. However, the national government is reluctant to adopt them fully and local realities still hamper their integrated implementation. Displaced women, therefore, remain in an especially vulnerable position. This paper argues that gender-sensitive humanitarian interventions must take into account all of these complexities of scale and political process in order to make legal frameworks more effective at the local level. In these contexts, interventions should pay particular attention to strategies that contribute to transforming pre-existing gender regimes. PMID:20132270

  9. Imaging of small radioactive point source displacement

    A new technique for three dimensional recording of a patient mandibular movement is described. A small and harmless radioactive source is fixed at the point of interest. Using proper collimation, the motion of the point source is recorded via a gamma camera and minicomputer. Image enhancement techniques are used and physiological displacement is reproduced. We measured the vertical, lateral and protrusive envelopes of motion of a point on a tooth from a full denture set mounted on a semiadjustable articulator. All displacements were calibrated. Multiple sources in a single experiment may be recorded to describe the displacement of several points of interest. First experiments were run on patients. This method, derived from Nuclear Medicine techniques, offers a powerful tool of general interest for the tracking of dynamic events in many fields of Dental Medicine, for instance temporo-mandibular joint disfunction as well as Prosthetics. (author)

  10. Performance of displacement ventilation in practice

    Naidenov, K.; Pitchurov, G.; Langkilde, Gunnar;

    2002-01-01

    the major local discomfort in the rooms with displacement ventilation. Twenty-three percent of the occupants were daily bothered by draught. In some buildings the maintenance personnel tried to improve occupants´ thermal comfort by raising the supply air temperature or office workers themselves......This paper presents results of a field study in offices with displacement ventilation. It comprises detailed physical measurements of the thermal environment and collection of occupants´ response at 227 workplaces. The results, both physical measurements and human response, identified draught as...... blocked the diffusers by rearranging the furniture. Half of the surveyed occupants were not satisfied with the indoor air quality. The main conclusion is that displacement ventilation needs careful design and room furnishing in order to ensure a comfortable environment. Occupants must understand the...

  11. Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2016-09-01

    Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM. PMID:27607281

  12. DNA fork displacement rates in human cells

    DNA fork displacement rates were measured in 20 human cell lines by a bromodeoxyuridine-313 nm photolysis technique. Cell lines included representatives of normal diploid, Fanconi's anemia, ataxia telangiectasia, xeroderma pigmentosum, trisomy-21 and several transformed lines. The average value for all the cell lines was 0.53 +- 0.08 μm/min. The average value for individual cell lines, however, displayed a 30% variation. Less than 10% of variation in the fork displacement rate appears to be due to the experimental technique; the remainder is probably due to true variation among the cell types and to culture conditions. (Auth.)

  13. Bucket Foundation Response Under Various Displacement Rates

    Vaitkunaite, Evelina; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo

    2016-01-01

    The present testing program aims at showing the pore pressure response around a bucket foundation skirt as well as the load and displacement change due to ten different displacement rates. Research findings are useful for a numerical model calibration focusing on the design of the upwind foundation...... in a multi-bucket foundation system. The foundation model is at a scale of approximately 1:20 prototype foundation size. The tests are performed in a pressure tank with the foundation model installed in dense sand. Based on the data, the conclusion is that the bucket foundation design in a storm case...

  14. Field measurement of relative ground displacement

    Protection of existing structures is a major requirement during underground nuclear blasts detonated as part of the Plowshare Program. Instrumental arrays to record ground motion are routinely established prior to blasts. These provide data on particle motions during the event but do not provide direct information concerning ground strains and relative displacements which may effect bridges, buildings, irrigation channels and other structures with large plan dimension. An experimental technique which was hastily developed and deployed to measure relative displacements during the Rio Blanco event of May 17, 1973 is described. The work was performed in anticipation of the Project Wagon Wheel in an area of Wyoming with many concrete lined irrigation channels

  15. Fundamental studies of pulsed laser ablation

    Claeyssens, F

    2001-01-01

    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  16. Percutaneous tumor ablation in medical radiology

    Vogl, T.J.; Mack, M.G. [University Hospital Frankfurt Univ. (Germany). Inst. for Diagnostic and Interventional Radiology; Helmberger, T.K. [Klinikum Bogenhausen, Academic Teaching Hospital of the Technical Univ. Munich (Germany). Dept. for Diagnostic and Interventional Radiology and Nuclear Medicine; Reiser, M.F. (eds.) [University Hospitals - Grosshadern and Innenstadt Munich Univ. (Germany). Dept. of Clinical Radiology

    2008-07-01

    Thermal ablation has become an integral part of oncology, especially in the field of interventional oncology. This very comprehensive book encompasses the different technologies employed in thermal ablation, its indications and the results achieved in various clinical conditions. The first part of the book clearly explains the basics of thermal ablative techniques such as laser-induced thermotherapy, radiofrequency ablation, microwave ablation, cryotherapy, and localized tumor therapy. The latest developments in the application of minimally invasive therapies in localized neoplastic disease are demonstrated. In the main part of the book, techniques of guiding the applicators to the target structures by use of different imaging tools such as ultrasound, computed tomography and magnetic resonance imaging are discussed. The results are presented for a variety of clinical indications, including liver and lung tumors and metastases and some rather rare conditions involving the kidney, the head and neck, the prostate, and soft tissue structures. A large number of acknowledged experts have contributed to the book, which benefits from a lucid structure and excellent images. (orig.)

  17. Fracture in Phenolic Impregnated Carbon Ablator

    Agrawal, Parul; Chavez-Garcia, Jose; Pham, John

    2013-01-01

    This paper describes the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of this research is on the class of materials known as phenolic impregnated carbon ablators. It has successfully flown on the Stardust spacecraft and is the thermal protection system material chosen for the Mars Science Laboratory and SpaceX Dragon spacecraft. Although it has good thermal properties, structurally, it is a weak material. To understand failure mechanisms in carbon ablators, fracture tests were performed on FiberForm(Registered TradeMark) (precursor), virgin, and charred ablator materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the tensile strength and toughness. It was observed that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred carbon ablators, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred carbon ablators showed greater strength values compared with FiberForm samples, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

  18. Percutaneous tumor ablation in medical radiology

    Thermal ablation has become an integral part of oncology, especially in the field of interventional oncology. This very comprehensive book encompasses the different technologies employed in thermal ablation, its indications and the results achieved in various clinical conditions. The first part of the book clearly explains the basics of thermal ablative techniques such as laser-induced thermotherapy, radiofrequency ablation, microwave ablation, cryotherapy, and localized tumor therapy. The latest developments in the application of minimally invasive therapies in localized neoplastic disease are demonstrated. In the main part of the book, techniques of guiding the applicators to the target structures by use of different imaging tools such as ultrasound, computed tomography and magnetic resonance imaging are discussed. The results are presented for a variety of clinical indications, including liver and lung tumors and metastases and some rather rare conditions involving the kidney, the head and neck, the prostate, and soft tissue structures. A large number of acknowledged experts have contributed to the book, which benefits from a lucid structure and excellent images. (orig.)

  19. Imaging in percutaneous ablation for atrial fibrillation

    Maksimovic, Ruzica [Erasmus Medical Center, Department of Radiology, GD Rotterdam (Netherlands); Institute for Cardiovascular Diseases of the University Medical Center, Belgrade (Czechoslovakia); Dill, Thorsten [Kerckhoff-Heart Center, Department of Cardiology, Bad Nauheim (Germany); Ristic, Arsen D.; Seferovic, Petar M. [Institute for Cardiovascular Diseases of the University Medical Center, Belgrade (Czechoslovakia)

    2006-11-15

    Percutaneous ablation for electrical disconnection of the arrhythmogenic foci using various forms of energy has become a well-established technique for treating atrial fibrillation (AF). Success rate in preventing recurrence of AF episodes is high although associated with a significant incidence of pulmonary vein (PV) stenosis and other rare complications. Clinical workup of AF patients includes imaging before and after ablative treatment using different noninvasive and invasive techniques such as conventional angiography, transoesophageal and intracardiac echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI), which offer different information with variable diagnostic accuracy. Evaluation before percutaneous ablation involves assessment of PVs (PV pattern, branching pattern, orientation and ostial size) to facilitate position and size of catheters and reduce procedure time as well as examining the left atrium (presence of thrombi, dimensions and volumes). Imaging after the percutaneous ablation is important for assessment of overall success of the procedure and revealing potential complications. Therefore, imaging methods enable depiction of PVs and the anatomy of surrounding structures essential for preprocedural management and early detection of PV stenosis and other ablation-related procedures, as well as long-term follow-up of these patients. (orig.)

  20. Imaging in percutaneous ablation for atrial fibrillation

    Percutaneous ablation for electrical disconnection of the arrhythmogenic foci using various forms of energy has become a well-established technique for treating atrial fibrillation (AF). Success rate in preventing recurrence of AF episodes is high although associated with a significant incidence of pulmonary vein (PV) stenosis and other rare complications. Clinical workup of AF patients includes imaging before and after ablative treatment using different noninvasive and invasive techniques such as conventional angiography, transoesophageal and intracardiac echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI), which offer different information with variable diagnostic accuracy. Evaluation before percutaneous ablation involves assessment of PVs (PV pattern, branching pattern, orientation and ostial size) to facilitate position and size of catheters and reduce procedure time as well as examining the left atrium (presence of thrombi, dimensions and volumes). Imaging after the percutaneous ablation is important for assessment of overall success of the procedure and revealing potential complications. Therefore, imaging methods enable depiction of PVs and the anatomy of surrounding structures essential for preprocedural management and early detection of PV stenosis and other ablation-related procedures, as well as long-term follow-up of these patients. (orig.)

  1. A Simple Condition for Bounded Displacement

    Solomon, Yaar

    2011-01-01

    We study separated nets that correspond to substitution tilings of the Euclidean space. We give a simple condition, in terms of the eigenvalues and eigenspaces of the substitution matrix, to know whether the separated net is a bounded displacement of the integer lattice or not.

  2. Nonlinear Brownian motion - mean square displacement

    W.Ebeling

    2004-01-01

    Full Text Available The stochastic dynamics of self-propelled Brownian particles is studied by means of the Langevin and the Fokker-Planck approach. We model the driving by a nonlinear friction function which has a negative part at small velocities, leading to active Brownian motion of the particles. The mean square displacement is estimated analytically and compared with numerical simulations.

  3. Education: protecting the rights of displaced children

    Suba Mahalingam

    2002-10-01

    Full Text Available UNICEF and its partners work with displaced communitiesto provide material assistance and protection, using as their basis the UN Convention on the Rights of the Child1 and other internationallegal instruments. Education has proven a valuable tool in this effort, not only making children aware of their rights but also providing a way to participate in the realisation of these rights.

  4. Wien's Displacement Law in Rindler Space

    De, Sanchari; Ghosh, Sutapa; Chakrabarty, Somenath

    2015-01-01

    In this article we have developed a formalism to obtained the modified form of Wien's displacement law when the wall of the enclosure containing a photon gas is expanding adiabatically with a uniform acceleration. We have also studied the gravitational redshift of photons inside the enclosure using the prescription of extended relativistic dynamics with an upper limit of acceleration.

  5. Displacement Damage in Bipolar Linear Integrated Circuits

    Rax, B. G.; Johnston, A. H.; Miyahira, T.

    2000-01-01

    Although many different processes can be used to manufacture linear integrated circuits, the process that is used for most circuits is optimized for high voltage -- a total power supply voltage of about 40 V -- and low cost. This process, which has changed little during the last twenty years, uses lateral and substrate p-n-p transistors. These p-n-p transistors have very wide base regions, increasing their sensitivity to displacement damage from electrons and protons. Although displacement damage effects can be easily treated for individual transistors, the net effect on linear circuits can be far more complex because circuit operation often depends on the interaction of several internal transistors. Note also that some circuits are made with more advanced processes with much narrower base widths. Devices fabricated with these newer processes are not expected to be significantly affected by displacement damage for proton fluences below 1 x 10(exp 12) p/sq cm. This paper discusses displacement damage in linear integrated circuits with more complex failure modes than those exhibited by simpler devices, such as the LM111 comparator, where the dominant response mode is gain degradation of the input transistor. Some circuits fail catastrophically at much lower equivalent total dose levels compared to tests with gamma rays. The device works satisfactorily up to nearly 1 Mrad(Si) when it is irradiated with gamma rays, but fails catastrophically between 50 and 70 krad(Si) when it is irradiated with protons.

  6. Passive Smoking in a Displacement Ventilated Room

    Bjørn, Erik; Nielsen, Peter V.

    The aim of this research is to see if the displacement ventilation principle can protect a person from exposure to passive tobacco smoking. This is done by full-scale experiments with two breathing thermal manikins, smoke visualisations, and tracer gas measurements. In some situations, exhaled sm...... convective boundary layer flow around the body....

  7. Microwave ablation versus laser ablation in occluding lateral veins in goats.

    Wang, Xu-hong; Wang, Xiao-ping; Su, Wen-juan; Yuan, Yuan

    2016-02-01

    Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation (EVLA) is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation (EMA). This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA (EMA group), and the rest 6 with EVLA (EVLA group). Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points: before, immediately after, 24 h (and 48 h) after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month(s) after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats. PMID:26838749

  8. Complete regeneration of ablated eyestalk in penaeid prawn, Penaeus monodon

    Desai, U.M.; Achuthankutty, C.T.

    Ablation of one eyestalk is generally practised in all commercial prawn hatcheries to induce gonad maturation and spawning. An observation was made that the ablated eyestalk of spent females of the tiger prawn Penaeus monodon was completely...

  9. Deep Dive Topic: Choosing between ablators

    Recent data on implosions using identical hohlraums and very similar laser drives underscores the conundrum of making a clear choice of one ablator over another. Table I shows a comparison of Be and CH in a nominal length, gold, 575 μm-diameter, 1.6 mg/cc He gas-fill hohlraum while Table II shows a comparison of undoped HDC and CH in a +700 length, gold, 575 μm diameter, 1.6 mg/cc He gas fill hohlraum. As can be seen in the tables, the net integrated fusion performance of these ablators is the same to within error bars. In the case of the undoped HDC and CH ablators, the hot spot shapes of the implosions were nearly indistinguishable for the experiments listed in Table II.

  10. Image-Guided Spinal Ablation: A Review.

    Tsoumakidou, Georgia; Koch, Guillaume; Caudrelier, Jean; Garnon, Julien; Cazzato, Roberto Luigi; Edalat, Faramarz; Gangi, Afshin

    2016-09-01

    The image-guided thermal ablation procedures can be used to treat a variety of benign and malignant spinal tumours. Small size osteoid osteoma can be treated with laser or radiofrequency. Larger tumours (osteoblastoma, aneurysmal bone cyst and metastasis) can be addressed with radiofrequency or cryoablation. Results on the literature of spinal microwave ablation are scarce, and thus it should be used with caution. A distinct advantage of cryoablation is the ability to monitor the ice-ball by intermittent CT or MRI. The different thermal insulation, temperature and electrophysiological monitoring techniques should be applied. Cautious pre-procedural planning and intermittent intra-procedural monitoring of the ablation zone can help reduce neural complications. Tumour histology, patient clinical-functional status and life-expectancy should define the most efficient and least disabling treatment option. PMID:27329231

  11. Deep Dive Topic: Choosing between ablators

    Hurricane, O. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thomas, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Olson, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-14

    Recent data on implosions using identical hohlraums and very similar laser drives underscores the conundrum of making a clear choice of one ablator over another. Table I shows a comparison of Be and CH in a nominal length, gold, 575 μm-diameter, 1.6 mg/cc He gas-fill hohlraum while Table II shows a comparison of undoped HDC and CH in a +700 length, gold, 575 μm diameter, 1.6 mg/cc He gas fill hohlraum. As can be seen in the tables, the net integrated fusion performance of these ablators is the same to within error bars. In the case of the undoped HDC and CH ablators, the hot spot shapes of the implosions were nearly indistinguishable for the experiments listed in Table II.

  12. Laser ablated hard coating for microtools

    McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

  13. Thermal Ablation Modeling for Silicate Materials

    Chen, Yih-Kanq

    2016-01-01

    A thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in ablation simulations of the meteoroid or glassy Thermal Protection Systems for spacecraft. Time-dependent axi-symmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. For model validation, the surface recession of fused amorphous quartz rod is computed, and the recession predictions reasonably agree with available data. The present parametric studies for two groups of meteoroid earth entry conditions indicate that the mass loss through moving molten layer is negligibly small for heat-flux conditions at around 1 MW/cm(exp. 2).

  14. Unexplained liver laceration after metastasis radiofrequency ablation

    Esther U(n)a; Javier Trueba; Jose Manuel Montes

    2009-01-01

    Many studies have established the role of radiofrequency (RF) ablation as a minimally invasive treatment for liver metastases. Although relatively safe, several complications have been reported with the increased use of RF ablation. We describe here a case of unexplained liver laceration after a RF procedure. A woman who presented a solitary metachronous liver metastasis underwent RF ablation treatment for this lesion. Six hours later the patient displayed fatigue and pallor.Emergency blood tests showed a haemoglobin level of < 7 g/dL and markedly elevated transaminase levels.A computed tomography examination revealed two areas of liver laceration with haematoma, one of them following the path of the needle and the other leading away from the first. Following a blood transfusion, the patient was haemodynamically stable and completely recovered 24 h later. The patient remained in bed for 1 wk. No surgical intervention was required, and she was discharged 1 wk later.

  15. Laser ablation of the protein lysozyme

    Schou, Jørgen; Canulescu, Stela; Amoruso, Salvatore; Wang, X.; Bruzzese, R.; Matei, Andreea; Constantinescu, Catalin; Dinescu, M.

    mechanics by laser impact. Samples of pressed lysozyme prepared in the same manner as in ns-experiments have been irradiated at 527 nm with >>300-fs pulses and at a similar fluence as in ns ablation. Even though the pulse energy was much smaller, there was a considerable ablation weight loss of lysozyme...... from each shot. This is the first time the ablation by fs-lasers of a protein has been recorded quantitatively. Films of lysozyme produced by fs-laser irradiation were analyzed by MALDI and a significant number of intact......Lysozyme is a well-known protein, which is used in food processing because of its bactericidal properties. The mass (14307 amu) is in the range in which it easily can be monitored by mass spectrometric methods, for example by MALDI (Matrix assisted laser desorption ionization). We have recently...

  16. Laser systems for ablative fractional resurfacing

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    Ablative fractional resurfacing (AFR) creates microscopic vertical ablated channels that are surrounded by a thin layer of coagulated tissue, constituting the microscopic treatment zones (MTZs). AFR induces epidermal and dermal remodeling, which raises new possibilities for the treatment of a...... variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional...... ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities with...

  17. Interactive Volumetry Of Liver Ablation Zones

    Egger, Jan; Brandmaier, Philipp; Seider, Daniel; Gawlitza, Matthias; Strocka, Steffen; Voglreiter, Philip; Dokter, Mark; Hofmann, Michael; Kainz, Bernhard; Hann, Alexander; Chen, Xiaojun; Alhonnoro, Tuomas; Pollari, Mika; Schmalstieg, Dieter; Moche, Michael

    2015-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm's results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each o...

  18. Advances in Imaging for Atrial Fibrillation Ablation

    Over the last fifteen years, our understanding of the pathophysiology of atrial fibrillation (AF) has paved the way for ablation to be utilized as an effective treatment option. With the aim of gaining more detailed anatomical representation, advances have been made using various imaging modalities, both before and during the ablation procedure, in planning and execution. Options have flourished from procedural fluoroscopy, electro anatomic mapping systems, pre procedural computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and combinations of these technologies. Exciting work is underway in an effort to allow the electro physiologist to assess scar formation in real time. One advantage would be to lessen the learning curve for what are very complex procedures. The hope of these developments is to improve the likelihood of a successful ablation procedure and to allow more patients access to this treatment

  19. Forced Displacement : Moving from Managing Risk to Facilitating Opportunity

    Lakhani, Sadaf

    2013-01-01

    Displacement is most commonly perceived as a situation of crisis; a time in which risks to the displaced and to host communities need to be mitigated and managed. However, if managed well, displacement can also bring new opportunities for the displaced and host communities to improve their lives. This paper looks at the predominant reasons why displacement is viewed and assisted by the aid community as a humanitarian issue, rather than as a phenomenon for which development thinking and develo...

  20. Symptomatic improvement after radiofrequency catheter ablation for typical atrial flutter

    O'Callaghan, P.; Meara, M; Kongsgaard, E; Poloniecki, J.; Luddington, L; Foran, J; Camm, A; Rowland, E; Ward, D.

    2001-01-01

    OBJECTIVE—To assess the changes in quality of life, arrhythmia symptoms, and hospital resource utilisation following catheter ablation of typical atrial flutter.
DESIGN—Patient questionnaire to compare the time interval following ablation with a similar time interval before ablation.
SETTING—Tertiary referral centre.
PATIENTS—63 consecutive patients were studied. Four patients subsequently underwent an ablate and pace procedure, two died of co-morbid illnesses, and two were lost to follow up....

  1. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    Baek, Jung Hwan; Lee, Jeong Hyun [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Valcavi, Roberto [Endocrinology Division and Thyroid Disease Center, Arcispedale Santa Maria Nuova, Reggio Emilia (Italy); Pacella, Claudio M. [Diagnostic Imaging and Interventional Radiology Department, Ospedale Regina Apostolorum, Albano Laziale-Rome (IT); Rhim, Hyun Chul [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Na, Dong Kyu [Human Medical Imaging and Intervention Center, Seoul (Korea, Republic of)

    2011-10-15

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

  2. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    Baek, Jung Hwan; Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

    2011-01-01

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

  3. Laser ablation of hepatocellular carcinoma-A review

    Gough-Palmer, Antony Lawrence; Gedroyc, Wladyslaw Michal Witold

    2008-01-01

    A wide range of local thermal ablative therapies have been developed in the treatment of non resectable hepatocellular carcinoma (HCC) in the last decade. Laser ablation (LA) and radiofrequency ablation (RFA) are the two most widely used of these. This article provides an up to date overview of the role of laser ablation in the local treatment of HCC. General principles, technique, image guidance and patient selection are discussed. A review of published data on treatment efficacy, long term ...

  4. Ablation driven by hot electrons in shock ignition

    Piriz, A. R.; Rodriguez Prieto, G.; Tahir, N. A.; Zhao, Y. T.

    2016-03-01

    An analytical model for the ablation driven by hot electrons is developed. The hot electrons are assumed to carry on the totality of the absorbed laser energy. Efficient energy coupling requires to keep the critical surface sufficiently close to the ablation front. To achieve this goal for high laser intensities a short enough laser wavelength is required. Scaling laws for the ablation pressure and the other relevant magnitudes of the ablation cloud are found in terms of the laser and target parameters.

  5. Quantifying Local Stiffness Variations in Radiofrequency Ablations with Dynamic Indentation

    DeWall, Ryan J.; Varghese, Tomy; Brace, Christopher L.

    2011-01-01

    Elastographic imaging can be used to monitor ablation procedures, however confident and clear determination of the ablation boundary is essential to ensure complete treatment of the pathological target. To investigate the potential for ablation boundary representation on elastographic images, local variations in the viscoelastic properties in radiofrequency ablated regions that were formed in vivo in porcine liver tissue were quantified using dynamic indentation. Spatial stiffness maps were t...

  6. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

    2014-12-02

    In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

  7. Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation

    Christensen, Bo Toftmann; Doggett, B.; Budtz-Jørgensen, C.; Schou, Jørgen; Lunney, J.G.

    2013-01-01

    The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at ~2 J cm-2 has been studied using angle-resolved Langmuir ion probe and thin film deposition techniques. For the same laser fluence, the time-of-flight ion signals from femtosecond and nanosecond laser ablation are similar; both show a singly peaked time-of-flight distribution. The angular distribution of ion emission and the deposition are well described by the adiabatic and isentropic model of plume ex...

  8. Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation

    A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm2. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown

  9. Kilohertz laser ablation for doping helium nanodroplets

    Mudrich, M; Müller, S; Dvorak, M; Buenermann, O; Stienkemeier, F

    2007-01-01

    A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam-depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the non-volatile DNA basis Guanine is found to be efficient and a number of oligomers are detected.

  10. Utilization of an ultrasound beam steering angle for measurements of tissue displacement vector and lateral displacement

    Chikayoshi Sumi

    2010-09-01

    Full Text Available Chikayoshi SumiDepartment of Information and Communication Sciences, Faculty of Science and Technology, Sophia University, Tokyo, JapanAbstract: A number of ultrasonic displacement/velocity measurement methods have been extensively developed for measurements of blood flow, tissue motion, and strain. Lateral modulation (LM methods have also been reported using steered, crossed beams, and these methods permit measurements of displacement vectors. In this report, a new beam steering method for the transmission and reception of ultrasound is proposed, which can enable measurements of lateral displacements and of arbitrary displacement vectors with a very high degree of accuracy. Because this beam steering method uses only a steering angle, this method is referred to as ASTA. With ASTA, the number of available methods to obtain a displacement vector measurement is limited to previously developed block-matching methods, such as the multidimensional cross-spectrum phase gradient method, and the multidimensional autocorrelation method (MAM and the multidimensional Doppler method (MDM using a block-matching method (the methods using block matching are referred to as MAMb and MDMb, respectively. Being dependent on the measurement method, only a lateral displacement measurement can be made even if the methods are multidimensional, ie, previously developed MAM and MDM using a moving average and a mirror setting of the obtained steered beams, and one-dimensional (1D, such as an autocorrelation method. Considerations of beamforming schemes using LM and ASTA show that the simple ASTA beamforming method increases capabilities for real-time measurements and requires a small physical aperture when compared with LM. For lateral displacement measurements (eg, blood flow in a carotid artery, a lateral coordinate must correspond to the direction of the target’s lateral motion, and the steering angle used is as large as possible to increase the measurement accuracy

  11. Treatment of colorectal metastases: surgery, cryotherapy, or radiofrequency ablation

    Primrose, J N

    2002-01-01

    The liver is the most common site of metastases from colorectal cancer. There has therefore been growing interest in how liver metastases may be ablated. The most common techniques for ablation of liver metastases are surgical resection, cryotherapy, and increasingly in recent years, radiofrequency ablation.

  12. Cardiac ablation by transesophageal high intensity focused ultrasound

    JIANG Chen-xi; YU Rong-hui; MA Chang-sheng

    2010-01-01

    @@ Cardiac ablation is an important modality of invasive therapy in modern cardiology, especially in the treatment of arrhythmias, as well as other diseases such as hypertrophic obstructive cardiomyopathy (HOCM). Since Huang et al1 used radiofrequency (RF) to ablate canine atrial ventricular junction, RF has developed into the leading energy source in catheter ablation of arrhythmias.

  13. Monitoring of tumor radio frequency ablation using derivative spectroscopy

    Spliethoff, J.W.; Tanis, E.; Evers, Daniel James; Hendriks, B.H.; Prevoo, W.; Ruers, T.J.M.

    2014-01-01

    Despite the widespread use of radio frequency (RF) ablation, an effective way to assess thermal tissue damage during and after the procedure is still lacking. We present a method for monitoring RF ablation efficacy based on thermally induced methemoglobin as a marker for full tissue ablation. Diffus

  14. Experimental measurement of ablation effects in plasma armature railguns

    Parker, J.V.; Parsons, W.M.

    1986-01-01

    Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma armature dynamics is proposed which incorporates the restrike process.

  15. Ablation techniques for primary and metastatic liver tumors.

    Ryan, Michael J; Willatt, Jonathon; Majdalany, Bill S; Kielar, Ania Z; Chong, Suzanne; Ruma, Julie A; Pandya, Amit

    2016-01-28

    Ablative treatment methods have emerged as safe and effective therapies for patients with primary and secondary liver tumors who are not surgical candidates at the time of diagnosis. This article reviews the current literature and describes the techniques, complications and results for radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation. PMID:26839642

  16. The Evolution of Tissue Stiffness at Radiofrequency Ablation Sites During Lesion Formation and in the Peri‐Ablation Period

    Eyerly, Stephanie A.; VEJDANI‐JAHROMI, MARYAM; Dumont, Douglas M.; Trahey, Gregg E.; Wolf, Patrick D.

    2015-01-01

    Peri‐Ablation Monitoring of RFA Lesion Stiffness Introduction Elastography imaging can provide radiofrequency ablation (RFA) lesion assessment due to tissue stiffening at the ablation site. An important aspect of assessment is the spatial and temporal stability of the region of stiffness increase in the peri‐ablation period. The aim of this study was to use 2 ultrasound‐based elastography techniques, shear wave elasticity imaging (SWEI) and acoustic radiation force impulse (ARFI) imaging, to ...

  17. Real-time Monitoring of High Intensity Focused Ultrasound (HIFU) Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound (HMIFU).

    Grondin, Julien; Payen, Thomas; Wang, Shutao; Konofagou, Elisa E

    2015-01-01

    Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a technique that can perform and monitor high-intensity focused ultrasound (HIFU) ablation. An oscillatory motion is generated at the focus of a 93-element and 4.5 MHz center frequency HIFU transducer by applying a 25 Hz amplitude-modulated signal using a function generator. A 64-element and 2.5 MHz imaging transducer with 68kPa peak pressure is confocally placed at the center of the HIFU transducer to acquire the radio-frequency (RF) channel data. In this protocol, real-time monitoring of thermal ablation using HIFU with an acoustic power of 7 W on canine livers in vitro is described. HIFU treatment is applied on the tissue during 2 min and the ablated region is imaged in real-time using diverging or plane wave imaging up to 1,000 frames/second. The matrix of RF channel data is multiplied by a sparse matrix for image reconstruction. The reconstructed field of view is of 90° for diverging wave and 20 mm for plane wave imaging and the data are sampled at 80 MHz. The reconstruction is performed on a Graphical Processing Unit (GPU) in order to image in real-time at a 4.5 display frame rate. 1-D normalized cross-correlation of the reconstructed RF data is used to estimate axial displacements in the focal region. The magnitude of the peak-to-peak displacement at the focal depth decreases during the thermal ablation which denotes stiffening of the tissue due to the formation of a lesion. The displacement signal-to-noise ratio (SNRd) at the focal area for plane wave was 1.4 times higher than for diverging wave showing that plane wave imaging appears to produce better displacement maps quality for HMIFU than diverging wave imaging. PMID:26556647

  18. A review of the safety aspects of radio frequency ablation

    Abhishek Bhaskaran

    2015-09-01

    Full Text Available In light of recent reports showing high incidence of silent cerebral infarcts and organized atrial arrhythmias following radiofrequency (RF atrial fibrillation (AF ablation, a review of its safety aspects is timely. Serious complications do occur during supraventricular tachycardia (SVT ablations and knowledge of their incidence is important when deciding whether to proceed with ablation. Evidence is emerging for the probable role of prophylactic ischemic scar ablation to prevent VT. This might increase the number of procedures performed. Here we look at the various complications of RF ablation and also the methods to minimize them. Electronic database was searched for relevant articles from 1990 to 2015. With better awareness and technological advancements in RF ablation the incidence of complications has improved considerably. In AF ablation it has decreased from 6% to less than 4% comprising of vascular complications, cardiac tamponade, stroke, phrenic nerve injury, pulmonary vein stenosis, atrio-esophageal fistula (AEF and death. Safety of SVT ablation has also improved with less than 1% incidence of AV node injury in AVNRT ablation. In VT ablation the incidence of major complications was 5–11%, up to 3.4%, up to 1.8% and 4.1–8.8% in patients with structural heart disease, without structural heart disease, prophylactic ablations and epicardial ablations respectively. Vascular and pericardial complications dominated endocardial and epicardial VT ablations respectively. Up to 3% mortality and similar rates of tamponade were reported in endocardial VT ablation. Recent reports about the high incidence of asymptomatic cerebral embolism during AF ablation are concerning, warranting more research into its etiology and prevention.

  19. Ultrasound-guided percutaneous thermal ablation of hepatocellular carcinoma using microwave and radiofrequency ablation

    AIM: To investigate the therapeutic efficacy of thermal ablation for treatment of hepatocellular carcinoma (HCC) using microwave and radiofrequency (RF) energy application. MATERIALS AND METHODS: A total of 190 nodules in 97 patients (84 male, 13 female; mean age 53.4 years, range 24-74 years) with HCC were treated with microwave or RF ablation in the last 4 years. The applicators were introduced into the tumours under conscious analgesic sedation by intravenous administration of fentanyl citrate and droperidol and local anaesthesia in both thermal ablation procedures. The patients were then followed up with contrast-enhanced computed tomography (CT) to evaluate treatment response. Survival was analysed using the Kaplan-Meier method. RESULTS: Complete ablation was obtained in 92.6% (176/190) nodules. The complete ablation rates were 94.6% (106/112) in microwave ablation and 89.7% (70/78) in RF ablation. The complete ablation rates in tumours≤2.0, 2.1-3.9 and ≥4.0 cm were 93.1, 93.8 and 86.4%, respectively. Local recurrence was found in 9.5% nodules and the rates in tumours≤2.0, 2.1-3.9 and ≥4.0 cm in diameter were 3.4, 9.9 and 31.8%, respectively. In the follow-up period, 7.1% nodules ablated by microwave and 12.8% by RF presented local recurrence. The 1, 2 and 3-year distant recurrence-free survivals were 47.2, 34.9 and 31.0%, respectively. Estimated mean survival was 32 months, and 1, 2 and 3-year cumulative survivals were 75.6, 58.5, and 50.0%, respectively. One and 2 years survivals of Child-Pugh class A, B and C patients were 83.8 and 70.4%, 78.2 and 53.2%, 36.3 and 27.3%, respectively. CONCLUSION: Thermal ablation therapy by means of microwave and RF energy application is an effective and safe therapeutic technique for hepatocellular carcinoma. Large tumours can be completely ablated, but have a significantly higher risk of local recurrence at follow-up

  20. Ultrasound-guided percutaneous thermal ablation of hepatocellular carcinoma using microwave and radiofrequency ablation

    Xu, H.-X.; Xie, X.-Y.; Lu, M.-D. E-mail: lumd@21cn.com; Chen, J.-W.; Yin, X.-Y.; Xu, Z.-F.; Liu, G.-J

    2004-01-01

    AIM: To investigate the therapeutic efficacy of thermal ablation for treatment of hepatocellular carcinoma (HCC) using microwave and radiofrequency (RF) energy application. MATERIALS AND METHODS: A total of 190 nodules in 97 patients (84 male, 13 female; mean age 53.4 years, range 24-74 years) with HCC were treated with microwave or RF ablation in the last 4 years. The applicators were introduced into the tumours under conscious analgesic sedation by intravenous administration of fentanyl citrate and droperidol and local anaesthesia in both thermal ablation procedures. The patients were then followed up with contrast-enhanced computed tomography (CT) to evaluate treatment response. Survival was analysed using the Kaplan-Meier method. RESULTS: Complete ablation was obtained in 92.6% (176/190) nodules. The complete ablation rates were 94.6% (106/112) in microwave ablation and 89.7% (70/78) in RF ablation. The complete ablation rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm were 93.1, 93.8 and 86.4%, respectively. Local recurrence was found in 9.5% nodules and the rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm in diameter were 3.4, 9.9 and 31.8%, respectively. In the follow-up period, 7.1% nodules ablated by microwave and 12.8% by RF presented local recurrence. The 1, 2 and 3-year distant recurrence-free survivals were 47.2, 34.9 and 31.0%, respectively. Estimated mean survival was 32 months, and 1, 2 and 3-year cumulative survivals were 75.6, 58.5, and 50.0%, respectively. One and 2 years survivals of Child-Pugh class A, B and C patients were 83.8 and 70.4%, 78.2 and 53.2%, 36.3 and 27.3%, respectively. CONCLUSION: Thermal ablation therapy by means of microwave and RF energy application is an effective and safe therapeutic technique for hepatocellular carcinoma. Large tumours can be completely ablated, but have a significantly higher risk of local recurrence at follow-up.

  1. Effect of ablatant composition on the ablation of a fuelling pellet

    The single species neutral-shielding model for the ablation of a hydrogenic pellet is extended by considering the ablatant as a mixture of four species: molecular and atomic hydrogen, protons and electrons. Compared with the results of the frozen flow, (i.e. the single species molecular hydrogen gas model), results of the analysis showed that the presence of dissociation and ionization effects caused a marked difference of the ablatant state. The attenuations of the incoming electron energy and energy flux, however, are very much similar irrespective of whether the ablated flow is in a frozen or an equilibrium state. The scaling law of the pellet ablation rate with respect to the plasma state of Te, ne and the pellet radius remains the same; the ablation rate is reduced by approximately 15%. To examine the possible existence of a spherical shell around the pellet where most of the incoming electron energy is absorbed, a comparison is made between the local electron collisional mean free path and the electron Larmor radius. A critical field at the ionization radius is evaluated. An effective spherical energy-absorbing region exists when the local field strength is below the critical value. For a plasma state of low Te and ne, (where the ablatant is hardly ionized), and for one near the thermonuclear condition (where a highly dense ablatant exists near the pellet), the effective energy absorption region is nearly spherical. In view of the variation of the plasma temperature and density as well as the pellet radius during the penetration of a pellet in a tokamak discharge, the existence of such an effective spherical energy absorption region still requires further exploration. (author)

  2. Pre-Procedural Imaging to Direct Catheter Ablation of Atrial Fibrillation: Anatomy and Ablation Strategy.

    Moussa Mansour; Ruskin, Jeremy N; Suhny Abbara; Godtfred Holmvang; E. Kevin Heist

    2008-01-01

    Successful catheter ablation of atrial fibrillation (AF) requires a detailed understanding of left atrial anatomy in order to maximize the safety and efficacy of the procedure. Common and rare variants of left atrial and pulmonary venous anatomy have been described which can affect the optimal ablation strategy for each individual patient. These variants include the presence of a right or left middle pulmonary vein, a left or right common pulmonary vein, a common inferior pulmonary vein, a ri...

  3. Pre-Procedural Imaging to Direct Catheter Ablation of Atrial Fibrillation: Anatomy and Ablation Strategy

    E. Kevin Heist MD PhD; Godtfred Holmvang MD; Suhny Abbara MD; Jeremy N. Ruskin MD; Moussa Mansour MD

    2008-01-01

    Successful catheter ablation of atrial fibrillation (AF) requires a detailed understanding of left atrial anatomy in order to maximize the safety and efficacy of the procedure. Common and rare variants of left atrial and pulmonary venous anatomy have been described which can affect the optimal ablation strategy for each individual patient. These variants include the presence of a right or left middle pulmonary vein, a left or right common pulmonary vein, a common inferior pulmonary vein, a ri...

  4. Boron isotopic enrichment by displacement chromatography

    10B enriched boron is used in applications requiring high volumetric neutron absorption (absorption cross section- 3837 barn for thermal and 1 barn for 1 MeV fast neutron). It is used in fast breeder reactor (as control rod material), in neutron counter, in Boron Neutron Capture Therapy etc. Owing to very small separation factor, boron isotopic enrichment is a complex process requiring large number of separation stages. Heavy Water Board has ventured in industrial scale production of 10B enriched boron using Exchange Distillation Process as well as Ion Displacement Chromatography Process. Ion Displacement Chromatography process is used in Boron Enrichment Plant at HWP, Manuguru. It is based on isotopic exchange between borate ions (B(OH)4-) on anion exchange resin and boric acid passing through resin. The isotopic exchange takes place due to difference in zero point energy of 10B and 11B

  5. Charge-displacement analysis for excited states

    Ronca, Enrico, E-mail: enrico@thch.unipg.it; Tarantelli, Francesco, E-mail: francesco.tarantelli@unipg.it [Istituto CNR di Scienze e Tecnologie Molecolari, via Elce di Sotto 8, I-06123 Perugia (Italy); Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, via Elce di Sotto 8, I-06123 Perugia (Italy); Pastore, Mariachiara, E-mail: chiara@thch.unipg.it; Belpassi, Leonardo; De Angelis, Filippo [Istituto CNR di Scienze e Tecnologie Molecolari, via Elce di Sotto 8, I-06123 Perugia (Italy); Angeli, Celestino; Cimiraglia, Renzo [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Ferrara, via Borsari 46, I-44100 Ferrara (Italy)

    2014-02-07

    We extend the Charge-Displacement (CD) analysis, already successfully employed to describe the nature of intermolecular interactions [L. Belpassi et al., J. Am. Chem. Soc. 132, 13046 (2010)] and various types of controversial chemical bonds [L. Belpassi et al., J. Am. Chem. Soc. 130, 1048 (2008); N. Salvi et al., Chem. Eur. J. 16, 7231 (2010)], to study the charge fluxes accompanying electron excitations, and in particular the all-important charge-transfer (CT) phenomena. We demonstrate the usefulness of the new approach through applications to exemplary excitations in a series of molecules, encompassing various typical situations from valence, to Rydberg, to CT excitations. The CD functions defined along various spatial directions provide a detailed and insightful quantitative picture of the electron displacements taking place.

  6. Precision optical displacement measurements using biphotons

    Lyons, Kevin; Kwiat, Paul G; Jordan, Andrew N

    2016-01-01

    We propose and examine the use of biphoton pairs, such as those created in parametric down conversion or four-wave mixing, to enhance the precision and the resolution of measuring optical displacements by position-sensitive detection. We show that the precision of measuring a small optical beam displacement with this method can be significantly enhanced by the correlation between the two photons, given the same optical mode. The improvement is largest if the correlations between the photons are strong, and falls off as the biphoton correlation weakens. More surprisingly, we find that the smallest resolvable parameter of a simple split detector scales as the inverse of the number of biphotons for small biphoton number ("Heisenberg scaling"), because the Fisher information diverges as the parameter to be estimated decreases in value. One usually sees this scaling only for systems with many entangled degrees of freedom. We discuss the transition for the split-detection scheme to the standard quantum limit scalin...

  7. Monitoring Atrial Fibrillation After Catheter Ablation

    Giovanni B Forleo, MD PhD; MAssimo Moltrasio, MD; Michela Casella MD, PhD; Antonio Dello Russo MD, PhD; Getano Fassini, MD; Manfredi Tesauro, MD, PhD; Claudio Tondo, MD, PhD.

    2014-04-01

    Full Text Available Although catheter ablation is an effective treatment for recurrent atrial fibrillation (AF, there is no consensus on the definition of success or follow-up strategies. Symptoms are the major motivation for undergoing catheter ablation in patients with AF, however it is well known that reliance on perception of AF by patients after AF ablation results in an underestimation of recurrence of the arrhythmia. Because symptoms of AF occurrence may be misleading, a reliable assessment of rhythm outcome is essential for the definition of success in both clinical care and research trials. Continuous rhythm monitoring over long periods of time is superior to intermittent recording using external monitors to detect the presence of AF episodes and to quantify the AF burden. Today, new devices implanted subcutaneously using a minimally invasive technique have been developed for continuous AF monitoring. Implantable devices keep detailed information about arrhythmia recurrences and might allow identification of very brief episodes of AF, the significance of which is still uncertain. In particular, it is not known whether there is any critical value of daily AF burden that has a prognostic significance. This issue remains an area of active discussion, debate and investigation. Further investigation is required to determine if continuous AF monitoring with implantable devices is effective in reducing stroke risk and facilitating maintenance of sinus rhythm after AF ablation.

  8. Determining ablation depth using CT imaging

    Urzová, J.; Jelínek, Miroslav; Remsa, Jan; Vopálka, R.

    Kladno: CTU Faculty of Biomedical Engineering, 2015 - (Jelínek, M.). s. 17 ISBN 978-80-01-05809-1. [Progressive Biomedical Materials and Technologies 2015. 09.10.2015-10.10.2015, Kladno] Institutional support: RVO:68378271 Keywords : ablation depth * CT imaging * excimer laser Subject RIV: BM - Solid Matter Physics ; Magnetism

  9. NOVEL LASER ABLATION TECHNOLOGY FOR SURFACE DECONTAMINATION

    The objective of this project is to develop a novel Laser Ablation Decontamination in Liquid (LADIL) technology for surface decontamination and safe removal of radioactive and/or toxic contaminants. It aims to achieve more efficient surface decontamination without secondary conta...

  10. Bending diamonds by femtosecond laser ablation

    Balling, Peter; Esberg, Jakob; Kirsebom, Kim;

    2009-01-01

    We present a new method based on femtosecond laser ablation for the fabrication of statically bent diamond crystals. Using this method, curvature radii of 1 m can easily be achieved, and the curvature obtained is very uniform. Since diamond is extremely tolerant to high radiation doses, partly due...

  11. Nonfluoroscopic Ablation of Atrial Fibrillation Using Cryoballoon

    Mansour Razminia, M.D., F.A.C.C.; Hany Demo, M.D.; Carlos Arrieta-Garcia, M.D.;

    2014-10-01

    Full Text Available Background: The conventional method of cryoballoon ablation of atrial fibrillation involves the use of fluoroscopy for visual guidance. The use of fluoroscopy is accompanied by significant radiation risks to the patient and the medical staff. Herein, we report our experience in performing successful nonfluoroscopic pulmonary vein isolation using cryoballoon ablation in 5 consecutive patients with paroxysmal atrial fibrillation Methods and Results: Five consecutive patients with paroxysmal atrial fibrillation underwent cryoballoon ablation for pulmonary vein isolation using a nonfluoroscopic approach. Pre-procedural cardiac computed tomography or cardiac magnetic resonance imaging was not performed in any patient. A total of twenty pulmonary veins were identified and successfully isolated (100% with the guidance of intracardiac echocardiography and 3-dimensional electroanatomic mapping. No fluoroscopy was used for the procedures. There were no major procedural adverse events. Conclusion: In an unselected group of patients undergoing cryoballoon ablation, a nonfluoroscopic approach is feasible and can be performed safely and effectively while eliminating the risks associated with radiation to both the patient and the medical staff.

  12. The credit market consequences of job displacement

    Benjamin J. Keys

    2010-01-01

    This paper demonstrates the important role of job displacement in the household bankruptcy decision. I develop a dynamic, forward-looking model of unemployment and bankruptcy where persistent negative income shocks increase a household's likelihood of filing for bankruptcy both immediately and in the future. Consistent with the model's predictions, I find that households in the NLSY are 2.5 times more likely to file for bankruptcy in the year immediately following a job loss, at a rate of an ...

  13. Forced displacement in Colombia: Magnitude and causes

    Ana María Ibáñez

    2009-01-01

    The article describes the magnitude, geographical extent, and causes of forced populationdisplacements in Colombia. Forced migration in Colombia is a war strategy adopted by armed groups to strengthen territorial strongholds, weaken civilian support to the enemy, seize valuable lands, and produce and transport illegal drugs with ease. Forced displacement in Colombia today affects 3.5 million people. Equivalent to 7.8 percent of Colombia’s population, and second worldwide only to Sudan, this s...

  14. Environmentally-induced displacement and human security

    Terminski, Bogumil

    2012-01-01

    We can distinguish two general causes of internal displacement worldwide: 1. the impact of threats to and ensuing decline in the level of human security below that needed for normal existence in the homeland territory, 2. administrative compulsion to leave the current place of residence. Every year, at least tens of millions of people on all continents are forced to leave their places of residence. The predominant cause is the occurrence of natural disasters, creating the most dynamic categor...

  15. Ultra-High-Frequency Capacitive Displacement Sensor

    Vanzandt, Thomas R.; Kenny, Thomas W.; Kaiser, William J.

    1994-01-01

    Improved class of compact, high-resolution capacitive displacement sensors operates at excitation frequency of 915 MHz and measures about 7.5 by 4 by 2 centimeters. Contains commercially available 915-MHz oscillator and transmission-line resonator. Resonator contains stripline inductor in addition to variable capacitor. Ultrahigh excitation frequency offers advantages of resolution and frequency response. Not deleteriously affected by mechanical overdriving, or contact between electrodes.

  16. Two-Domain DNA Strand Displacement

    Luca Cardelli

    2010-01-01

    We investigate the computing power of a restricted class of DNA strand displacement structures: those that are made of double strands with nicks (interruptions) in the top strand. To preserve this structural invariant, we impose restrictions on the single strands they interact with: we consider only two-domain single strands consisting of one toehold domain and one recognition domain. We study fork and join signal-processing gates based on these structures, and we show that these systems are ...

  17. Relativistic Lagrangian displacement field and tensor perturbations

    Rampf, C.; Wiegand, A.

    2014-01-01

    We investigate the purely spatial Lagrangian coordinate transformation from the Lagrangian to the fundamental Eulerian frame. We demonstrate three techniques for extracting the relativistic displacement field from a given solution in the Lagrangian frame. These techniques are (a) from defining a local set of Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a specific gauge transformation; and (c) from a fully non-perturbative approach based on the ADM split. The la...

  18. Probing gaugino coannihilation with displaced vertex searches

    Nagata, Natsumi

    2016-01-01

    Bino-like dark matter in supersymmetric theories tends to suffer from over-production. This problem can be evaded if there is another gaugino which has a mass close to the bino mass so that it enhances the annihilation rate of bino dark matter through coannihilation. We study such possibilities in high-scale supersymmetric models, and show that searches for long-lived particles with displaced vertices can test the bino-gaugino coannihilation scenario in the forthcoming LHC experiments.

  19. Laser Measurement of Building Vibration and Displacement

    A.J. Bougard; B.R. Ellis

    2000-01-01

    This paper considers four laser systems used by the Building Research Establishment (BRE) to investigate the behaviour of structures. Lasers enable remote measurements of vibration and displacement to be taken where access to a structure is difficult or where fire, explosion or structural collapse creates a hazardous environment. Each system will be described, and its use illustrated using measurements taken on real structures.The four systems are:1. Laser Interferometer: This is used to meas...

  20. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  1. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  2. A chemical model of meteoric ablation

    T. Vondrak

    2008-07-01

    Full Text Available Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides, and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1 and smallest (10−17–10

  3. Thermochemical Ablation Analysis of the Orion Heatshield

    Sixel, William

    2015-01-01

    The Orion Multi-Purpose Crew Vehicle will one day carry astronauts to the Moon and beyond, and Orion's heatshield is a critical component in ensuring their safe return to Earth. The Orion heatshield is the structural component responsible for absorbing the intense heating environment caused by re-entry to Earth's atmosphere. The heatshield is primarily composed of Avcoat, an ablative material that is consumed during the re-entry process. Ablation is primarily characterized by two processes: pyrolysis and recession. The decomposition of in-depth virgin material is known as pyrolysis. Recession occurs when the exposed surface of the heatshield reacts with the surrounding flow. The Orion heatshield design was changed from an individually filled Avcoat honeycomb to a molded block Avcoat design. The molded block Avcoat heatshield relies on an adhesive bond to keep it attached to the capsule. In some locations on the heatshield, the integrity of the adhesive bond cannot be verified. For these locations, a mechanical retention device was proposed. Avcoat ablation was modelled in CHAR and the in-depth virgin material temperatures were used in a Thermal Desktop model of the mechanical retention device. The retention device was analyzed and shown to cause a large increase in the maximum bondline temperature. In order to study the impact of individual ablation modelling parameters on the heatshield sizing process, a Monte Carlo simulation of the sizing process was proposed. The simulation will give the sensitivity of the ablation model to each of its input parameters. As part of the Monte Carlo simulation, statistical uncertainties on material properties were required for Avcoat. Several properties were difficult to acquire uncertainties for: the pyrolysis gas enthalpy, non-dimensional mass loss rate (B´c), and Arrhenius equation parameters. Variability in the elemental composition of Avcoat was used as the basis for determining the statistical uncertainty in pyrolysis gas

  4. Ablation of Atrial Fibrillation: Patient Selection, Periprocedural Anticoagulation, Techniques, and Preventive Measures After Ablation.

    Link, Mark S; Haïssaguerre, Michel; Natale, Andrea

    2016-07-26

    Atrial fibrillation (AF) is the most common arrhythmia encountered by cardiologists and is a major cause of morbidity and mortality. Risk factors for AF include age, male sex, genetic predisposition, hypertension, diabetes mellitus, sleep apnea, obesity, excessive alcohol, smoking, hyperthyroidism, pulmonary disease, air pollution, heart failure, and possibly excessive exercise. The management of AF involves decisions about rate versus rhythm control. Asymptomatic patients are generally managed with rate control and anticoagulation. Symptomatic patients will desire rhythm control. Rhythm control options are either antiarrhythmic agents or ablation, with each having its own risks and benefits. Ablation of AF has evolved from a rare and complex procedure to a common electrophysiological technique. Selection of patients to undergo ablation is an important aspect of AF care. Patients with the highest success rates of ablation are those with normal structural hearts and paroxysmal AF, although those with congestive heart failure have the greatest potential benefit of the procedure. Although pulmonary vein isolation of any means/energy source is the approach generally agreed on for those with paroxysmal AF, optimal techniques for the ablation of nonparoxysmal AF are not yet clear. Anticoagulation reduces thromboembolic complications; the newer anticoagulants have eased management for both the patient and the cardiologist. Aggressive management of modifiable risk factors (hypertension, diabetes mellitus, sleep apnea, obesity, excessive alcohol, smoking, hyperthyroidism, pulmonary disease, air pollution, and possibly excessive exercise) after ablation reduces the odds of recurrent AF and is an important element of care. PMID:27462054

  5. Comparing Teaching Approaches About Maxwell's Displacement Current

    Karam, Ricardo; Coimbra, Debora; Pietrocola, Maurício

    2014-08-01

    Due to its fundamental role for the consolidation of Maxwell's equations, the displacement current is one of the most important topics of any introductory course on electromagnetism. Moreover, this episode is widely used by historians and philosophers of science as a case study to investigate several issues (e.g. the theory-experiment relationship). Despite the consensus among physics educators concerning the relevance of the topic, there are many possible ways to interpret and justify the need for the displacement current term. With the goal of understanding the didactical transposition of this topic more deeply, we investigate three of its domains: (1) The historical development of Maxwell's reasoning; (2) Different approaches to justify the term insertion in physics textbooks; and (3) Four lectures devoted to introduce the topic in undergraduate level given by four different professors. By reflecting on the differences between these three domains, significant evidence for the knowledge transformation caused by the didactization of this episode is provided. The main purpose of this comparative analysis is to assist physics educators in developing an epistemological surveillance regarding the teaching and learning of the displacement current.

  6. Vertical displacement and position control in tokamaks

    Free-boundary nearly rigid displacements are considered in a plasma confined by a magnetic field consisting of one part generated by the plasma current density, and one part being due to steady currents in fixed external conductors. An induced surface current effect and a related force on the plasma arise when the externally applied field is inhomogeneous in the direction of displacement. This additional force has not been taken into account in conventional MHD theory. In the particular case of tokamaks , the induced surface current effect has two impacts on vertical nearly rigid displacements. First, there arises an additional restoring force and a positive contribution to the change in potential energy when the externally applied field is inhomogeneous in the vertical direction. A special design of poloidal field coils can thus provide new means for vertical position control in tokamaks, also in the case of strongly elongated cross-sections. Second, an earlier simplified model, in which the plasma is represented by a line current, has to be modified since the plasma is a highly conducting body of finite size. 4 refs

  7. Contact Force and Atrial Fibrillation Ablation

    Waqas Ullah; Richard Schilling; Tom Wong

    2016-02-01

    Full Text Available Catheters able to measure the force and vector of contact between the catheter tip and myocardium are now available. Pre-clinical work has established that the degree of contact between the radiofrequency ablation catheter and myocardium correlates with the size of the delivered lesion. Excess contact is associated with steam pops and perforation. Catheter contact varies within the left atrium secondary to factors including respiration, location, atrial rhythm and the trans-septal catheter delivery technology used. Compared with procedures performed without contact force (CF-sensing, the use of this technology has, in some studies, been found to improve complication rates, procedure and fluoroscopy times, and success rates. However, for each of these parameters there are also studies suggesting a lack of difference from the availability of CF data. Nevertheless, CF-sensing technology has been adopted as a standard of care in many institutions. It is likely that use of CF-sensing technology will allow for the optimization of each individual radiofrequency application to maximize efficacy and procedural safety. Recent work has attempted to define what these optimal targets should be, and approaches to do this include assessing for sites of pulmonary vein reconnection after ablation, or comparing the impedance response to ablation. Based on such work, it is apparent that factors including mean CF, force time integral (the area under the force-time curve and contact stability are important determinants of ablation efficacy. Multicenter prospective randomized data are lacking in this field and required to define the CF parameters required to produce optimal ablation.

  8. Femtosecond laser ablation of brass in air and liquid media

    Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

  9. Tissue temperatures and lesion size during irrigated tip catheter radiofrequency ablation: an in vitro comparison of temperature-controlled irrigated tip ablation, power-controlled irrigated tip ablation, and standard temperature-controlled ablation

    Petersen, H H; Chen, X; Pietersen, A;

    2000-01-01

    The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced in the...... power-controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature-controlled irrigated tip ablation, comparing it with standard...... temperature-controlled ablation and power-controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature-controlled irrigated tip ablation at target temperatures 60 degrees C, 70 degrees C, and 80 degrees C with infusion of 1 mL saline/min were compared...

  10. Wavelength dependence of soft tissue ablation by using pulsed lasers

    Xianzeng Zhang; Shusen Xie; Qing Ye; Zhenlin Zhan

    2007-01-01

    Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear,sharp cuts following closely the patial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The blation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

  11. Ultrasonography for non-displaced and mini-displaced humeral lateral condyle fractures in children

    ZHANG Jing-dong; CHEN Hua

    2008-01-01

    Objective: To evaluate the value of ultrasonography in non-displaced and mini-displaced humeral lateral condyle fractures in children.Methods: Nine children aged 2-9 years with non-displaced or mini-displaced humeral lateral condyle fractures were examined by high-resolution ultrasonography.The fracture line through the joint surface was visualized by ultrasonography in 6 case,in which closed reduction and percutaneous pinning was performed on 3 patients and other 3 patients did not receive the treatment because of patients' or their parents'refusal.In the remaining 3 children,ultrasonography did not reveal the cartilaginous trochle involvement at the joint surface and conservative treatment was adopted.Results: The average follow-up period was 8 months.The sonographic findings were confirmed by magnetic resonance imaging in one child who received conservative treatment and another child who received percutaneous pinning.The elbow function and fractttre healing were good in cases received closed reduction and percutaneous pinning.Among the three cases who refused to receive closed reduction and internal f'txation,re-displacement occurred in 1 case and delayed union in 1 case.All three cases receiving conservative treatment had good results both in elbow function and fracture healing.Conclusion: High-resolution ultrasonography enable to reveal non-displaced and mini-displaced humeral lateral condyle fractures as well as to ascertain whether the cartilaginous trochlea humeri was involved.For these cases,arthrography or magnetic resonance imaging is unnecessary.

  12. Displacement Mechanism of Polymer Flooding by Molecular Tribology

    YANG Er-Long; SONG Kao-Ping

    2006-01-01

    @@ Whether polymer flooding can enhance displacement efficiency or not is still a problem under debate. Laboratory experiment, numerical simulation and core data analysis are the commonly used means to study polymer flooding displacement efficiency.

  13. Theoretical study on line source laser-induced surface acoustic waves in two-layer structure in ablative regime

    Shen, Z. H.; Xu, B. Q.; Ni, X. W.; Lu, J.; Zhang, S. Y.

    2004-03-01

    The generation of ultrasound in film-substrate system by a laser line source is studied in the case of ablation mechanism, which can be realized by adding a liquid layer at the excitation point. The time domain displacement can be yielded by the numerical jointed inversed Laplace-Fourier transformation technique. The typical surface acoustic waves (SAW) of two layer structures, slow film on fast substrate and fast film on slow substrate, are obtained and the effect of the propagation distance and the thickness of the film on the SAW are given.

  14. The effect of ethanol infusion on the size of the ablated lesion in radiofrequency thermal ablation: A pilot study

    Kim, Young Sun; Rhim, Hyun Chul; Koh, Byung Hee; Cho, On Koo; Seo, Heung Suk; Kim, Yong Soo; Joo, Kyoung Bin [Hanyang University College of Medicine, Seoul (Korea, Republic of)

    2001-09-15

    To assess the effect of ethanol infusion on the size of ablated lesion during radiofrequency (RF) thermal ablation. We performed an ex vivo experimental study using a total of 15 pig livers. Three groups were designed: 1)normal control (n=10), 2) saline infusion (n=10) 3) ethanol infusion (n=10). Two radiofrequency ablations were done using a 50 watt RF generator and a 15 guage expandable elections with four prongs in each liver. During ablation for 8 minutes, continuous infusion of fluid at a rate of 0.5 ml/min through the side arm of electrode was performed. We checked the frequency of the 'impeded-out' phenomenon due to abrupt increase of impedance during ablation. Size of ablated lesion was measured according to length, width, height, and subsequently volume after the ablations. The sizes of the ablated lesions were compared between the three groups. 'Impeded-out' phenomenon during ablation was noted 4 times in control group, although that never happened in saline or ethanol infusion groups. There were significant differences in the volumes of ablated lesions between control group (10.62 +- 1.45 cm{sup 3}) and saline infusion group (15.33 +- 2.47 cm{sup 3}), and saline infusion group and ethanol infusion group (18.78 +- 3.58 cm{sup 3}) (p<0.05). Fluid infusion during radiofrequency thermal ablation decrease a chance of charming and increase the volume of the ablated lesion. Ethanol infusion during ablation may induce larger volume of ablated lesion than saline infusion.

  15. Characterization of lesion formation and bubble activities during high-intensity focused ultrasound ablation using temperature-derived parameters

    Hsiao, Yi-Sing; Kumon, Ronald E.; Deng, Cheri X.

    2013-09-01

    Successful high-intensity focused ultrasound (HIFU) thermal tissue ablation relies on accurate information of the tissue temperature and tissue status. Often temperature measurements are used to predict and monitor the ablation process. In this study, we conducted HIFU ablation experiments with ex vivo porcine myocardium tissue specimens to identify changes in temperature associated with tissue coagulation and bubble/cavity formation. Using infrared (IR) thermography and synchronized bright-field imaging with HIFU applied near the tissue surface, parameters derived from the spatiotemporal evolution of temperature were correlated with HIFU-induced lesion formation and overheating, of which the latter typically results in cavity generation and/or tissue dehydration. Emissivity of porcine myocardium was first measured to be 0.857 ± 0.006 (n = 3). HIFU outcomes were classified into non-ablative, normal lesion, and overheated lesion. A marked increase in the rate of temperature change during HIFU application was observed with lesion formation. A criterion using the maximum normalized second time derivative of temperature change provided 99.1% accuracy for lesion identification with a 0.05 s-1 threshold. Asymmetric temperature distribution on the tissue surface was observed to correlate with overheating and/or bubble generation. A criterion using the maximum displacement of the spatial location of the peak temperature provided 90.9% accuracy to identify overheated lesion with a 0.16 mm threshold. Spatiotemporal evolution of temperature obtained using IR imaging allowed determination of the critical cumulative equivalent minutes at 43 °C (CEM43) for lesion formation to be 170 min. Similar temperature characteristics indicative of lesion formation and overheating were identified for subsurface HIFU ablation. These results suggest that parameters derived from temperature changes during HIFU application are associated with irreversible changes in tissue and may provide

  16. Black-box modeling to estimate tissue temperature during radiofrequency catheter cardiac ablation: feasibility study on an agar phantom model

    The aim of this work was to study linear deterministic models to predict tissue temperature during radiofrequency cardiac ablation (RFCA) by measuring magnitudes such as electrode temperature, power and impedance between active and dispersive electrodes. The concept involves autoregressive models with exogenous input (ARX), which is a particular case of the autoregressive moving average model with exogenous input (ARMAX). The values of the mode parameters were determined from a least-squares fit of experimental data. The data were obtained from radiofrequency ablations conducted on agar models with different contact pressure conditions between electrode and agar (0 and 20 g) and different flow rates around the electrode (1, 1.5 and 2 L min−1). Half of all the ablations were chosen randomly to be used for identification (i.e. determination of model parameters) and the other half were used for model validation. The results suggest that (1) a linear model can be developed to predict tissue temperature at a depth of 4.5 mm during RF cardiac ablation by using the variables applied power, impedance and electrode temperature; (2) the best model provides a reasonably accurate estimate of tissue temperature with a 60% probability of achieving average errors better than 5 °C; (3) substantial errors (larger than 15 °C) were found only in 6.6% of cases and were associated with abnormal experiments (e.g. those involving the displacement of the ablation electrode) and (4) the impact of measuring impedance on the overall estimate is negligible (around 1 °C)

  17. The Theme of Displacement in Contemporary Art

    John POTTS

    2012-03-01

    Full Text Available Cet article examine les images et idées de dislocation dans des œuvres d'art récentes. Le thème du déplacement ou de la dislocation est traité dans le contexte de l'aspect globalisant de l'art contemporain, considéré lui-même comme un reflet de la mondialisation. Les principaux textes théoriques qui influencent et informent les pratiques en matière de conservation sont abordés, entre autres les écrits de Giorgio Agamben, Nicolas Bourriaud et Rex Butler. Le thème de la dislocation dans l'art contemporain est analysé au travers des œuvres de nombreux artistes, tels que Francis Alÿs, Bill Fontana, Allan Sekula, Chen Chieh-jen, Ai Wei Wei, Rosemary Laing, Mike Parr, Santiago Sierra, Rebecca Belmore et Tracey Moffatt.This essay considers images and ideas of displacement in recent works of art. The theme of displacement is examined in the context of the globalist aspect of contemporary art, itself a reflection of globalisation. Influential theoretical texts informing curatorial practice and the discourse of contemporary art theory are discussed, including the writings of Girogio Agamben, Nicolas Bourriaud and Rex Butler. The theme of displacement in contemporary art is analysed with regard to the work of many artists, including Francis Alÿs, Bill Fontana, Allan Sekula, Chen Chieh-jen, Ai Wei Wei, Rosemary Laing, Mike Parr, Santiago Sierra, Rebecca Belmore and Tracey Moffatt.

  18. Year of displaced people’s rights in Colombia

    Marco Alberto Romero

    2007-01-01

    A Campaign for the Rights of Displaced People in Colombia, launched in 2007 by UNHCR, Colombian NGO CODHES and the Catholic Church, has tried to raise awareness in Colombia and the international community about the severity of the country’s displacement crisis and its failure to guarantee the rights of displaced people.

  19. 40 CFR 86.419-2006 - Engine displacement, motorcycle classes.

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Engine displacement, motorcycle... Emission Regulations for 1978 and Later New Motorcycles, General Provisions § 86.419-2006 Engine displacement, motorcycle classes. (a)(1) Engine displacement shall be calculated using nominal engine...

  20. 40 CFR 86.419-78 - Engine displacement, motorcycle classes.

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Engine displacement, motorcycle... Emission Regulations for 1978 and Later New Motorcycles, General Provisions § 86.419-78 Engine displacement, motorcycle classes. (a)(1) Engine displacement shall be calculated using nominal engine values and rounded...

  1. Displacer rod for use in a mechanical spectral shift reactor

    A displacer rod for use in a mechanical spectral shift pressurized water nuclear reactor comprises a sectioned substantially hollow low neutron absorbing metal rod capable of displacing reactor coolant without absorbing a high amount of neutrons. The tubular sections preferably consist of stainless steel and Zircaloy tubing interconnected by a solid Zircaloy metal rod and may contain pellets for weighting the displacer rod. (author)

  2. Two-Domain DNA Strand Displacement

    Luca Cardelli

    2010-06-01

    Full Text Available We investigate the computing power of a restricted class of DNA strand displacement structures: those that are made of double strands with nicks (interruptions in the top strand. To preserve this structural invariant, we impose restrictions on the single strands they interact with: we consider only two-domain single strands consisting of one toehold domain and one recognition domain. We study fork and join signal-processing gates based on these structures, and we show that these systems are amenable to formalization and to mechanical verification.

  3. Two-Domain DNA Strand Displacement

    Cardelli, Luca

    2010-01-01

    We investigate the computing power of a restricted class of DNA strand displacement structures: those that are made of double strands with nicks (interruptions) in the top strand. To preserve this structural invariant, we impose restrictions on the single strands they interact with: we consider only two-domain single strands consisting of one toehold domain and one recognition domain. We study fork and join signal-processing gates based on these structures, and we show that these systems are amenable to formalization and to mechanical verification.

  4. Simulating People Moving in Displacement Ventilated Rooms

    Mattsson, M.; Bjørn, Erik; Sandberg, M.; Nielsen, Peter V.

    A displacement ventilation system works better the more uni-directional the air flow through the ventilated room is: from floor to ceiling. Thus, from an air quality point of view, there should be as little vertical mixing of the room air as possible. It is therefore comprehensible that physical...... activity in the room -like peoples movements -in previous studies has been shown to influence the effectiveness of the ventilation. In this study we have compared results from previous tests, where a cylindrical person simulator was used, to results obtained when using a person simulator of more human...

  5. Mirror displacement energies and neutron skins

    Duflo, J

    2002-01-01

    Assuming isospin conservation, it is shown that a single expression accounts for both neutron and proton radii. Excellent fits to the former turn out to be consistent with different neutron skins. To fix their values the displacement energies between mirror nuclei, MDE, are calculated using an accurately derived Coulomb energy, and smooth averages of the charge symmetry breaking potentials constrained to state of the art values. Optimum agreement with observed MDE and neutron skins is obtained. The remaining uncertainties are shown to be due to shell effects.

  6. Dynamics and structure of energetic displacement cascades

    This paper summarizes recent progress in the understanding of energetic displacement cascades and the primary state of damage in metals. On the theoretical side, the availability of supercomputers has greatly enhanced our ability to simulate cascades by molecular dynamics. Recent application of this simulation technique to Cu and Ni provides new insight into the dynamics of cascade processes. On the experimental side, new data on ion beam mixing and in situ electron microscopy studies of ion damage at low temperatures reveal the role of the thermodynamic properties of the material on cascade dynamics and structure. 38 refs., 9 figs

  7. Ablation properties of carbon/carbon composites with tungsten carbide

    The ablation properties and morphologies of carbon/carbon (C/C) composites with tungsten carbide (WC) filaments were investigated by ablation test on an arc heater and scanning electron microscopy. And the results were compared with those without tungsten carbide (WC) filaments tested under the same conditions. It shows that there is a big difference between C/C composites with and without WC filaments on both macroscopic and microscopic ablation morphologies and the ablation rates of the former are higher than the latter. It is found that the ablation process of C/C composites with WC filaments includes oxidation of carbon fibers, carbon matrices and WC, melting of WC and WO3, and denudation of WC, WO3 and C/C composites. Oxidation and melting of WC leads to the formation of holes in z directional carbon fiber bundles, which increases the coarseness of the ablation surfaces of the composites, speeds up ablation and leads to the higher ablation rate. Moreover, it is further found that the molten WC and WO3 cannot form a continuous film on the ablation surface to prevent further ablation of C/C composites.

  8. Percutaneous thermal ablation of renal neoplasms; Perkutane Thermoablation von Nierentumoren

    Tacke, J. [Inst. fuer Diagnostische und Interventionelle Radiologie/Neuroradiologie, Klinikum Passau (Germany); Mahnken, A.H.; Guenther, R.W. [Klinik fuer Radiologische Diagnostik, Universitaetsklinikum Aachen (Germany)

    2005-12-15

    Due to modern examination techniques such as multidetector computed tomography and high-field magnetic resonance imaging, the detection rate of renal neoplasms is continually increasing. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that are possible neoplasms should be treated. Traditional treatment techniques include radical nephrectomy or nephron-sparing resection, which are increasingly performed laparoscopically. Modern thermal ablation techniques such as hyperthermal techniques like radiofrequency ablation RFA, laser induced thermal ablation LITT, focused ultrasound FUS and microwave therapy MW, as well as hypothermal techniques (cryotherapy) may be a useful treatment option for patients who are unfit for or refuse surgical resection. Cryotherapy is the oldest and best known thermal ablation technique and can be performed laparoscopically or percutaneously. Since subzero temperatures have no antistyptic effect, additional maneuvers must be performed to control bleeding. Percutaneous cryotherapy of renal tumors is a new and interesting method, but experience with it is still limited. Radiofrequency ablation is the most frequently used method. Modern probe design allows volumes between 2 and 5 cm in diameter to be ablated. Due to hyperthermal tract ablation, the procedure is deemed to be safe and has a low complication rate. Although there are no randomized comparative studies to open resection, the preliminary results for renal RFA are promising and show RFA to be superior to other thermal ablation techniques. Clinical success rates are over 90% for both, cryo- and radiofrequency ablation. Whereas laser induced thermal therapy is established in hepatic ablation, experience is minimal with respect to renal application. For lesions of more than 2 cm in diameter, additional cooling catheters are required. MR thermometry offers temperature control during ablation. Microwave ablation is characterized by small ablation volumes

  9. Automated planning of ablation targets in atrial fibrillation treatment

    Keustermans, Johannes; De Buck, Stijn; Heidbüchel, Hein; Suetens, Paul

    2011-03-01

    Catheter based radio-frequency ablation is used as an invasive treatment of atrial fibrillation. This procedure is often guided by the use of 3D anatomical models obtained from CT, MRI or rotational angiography. During the intervention the operator accurately guides the catheter to prespecified target ablation lines. The planning stage, however, can be time consuming and operator dependent which is suboptimal both from a cost and health perspective. Therefore, we present a novel statistical model-based algorithm for locating ablation targets from 3D rotational angiography images. Based on a training data set of 20 patients, consisting of 3D rotational angiography images with 30 manually indicated ablation points, a statistical local appearance and shape model is built. The local appearance model is based on local image descriptors to capture the intensity patterns around each ablation point. The local shape model is constructed by embedding the ablation points in an undirected graph and imposing that each ablation point only interacts with its neighbors. Identifying the ablation points on a new 3D rotational angiography image is performed by proposing a set of possible candidate locations for each ablation point, as such, converting the problem into a labeling problem. The algorithm is validated using a leave-one-out-approach on the training data set, by computing the distance between the ablation lines obtained by the algorithm and the manually identified ablation points. The distance error is equal to 3.8+/-2.9 mm. As ablation lesion size is around 5-7 mm, automated planning of ablation targets by the presented approach is sufficiently accurate.

  10. 3D Multifunctional Ablative Thermal Protection System

    Feldman, Jay; Venkatapathy, Ethiraj; Wilkinson, Curt; Mercer, Ken

    2015-01-01

    NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule is a 3-dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad serves first as a structural component and later as an ablative heat shield, partially consumed on Earth re-entry. This presentation will summarize the development of a new 3D quartz cyanate ester composite material, 3-Dimensional Multifunctional Ablative Thermal Protection System (3D-MAT), designed to meet the mission requirements for the Orion compression pad. Manufacturing development, aerothermal (arc-jet) testing, structural performance, and the overall status of material development for the 2018 EM-1 flight test will be discussed.

  11. Glycine Ablation during Comet/Meteoroid Impact

    Huo, Winifred M.; Dateo, Christopher E.; Mckay, Christopher P.; Borucki, William J.

    2004-01-01

    Amino acids and other organic compounds important to the chemistry of life are thought to have been delivered to early Earth by asteroids and comets. The survivability of such compounds upon high speed entry is not well understood. If molecular processing occurs during entry, the nature of the new molecules produced by such processing is also an open question. To address this question, we have initiated a study of the ablation of glycine, the simplest amino acid, upon the high speed entry of a comet or meteoroid into an atmosphere. The study assumes glycine is distributed on the surface of the comet/meteoroid. The high speed impact creates electrons, ions, and radicals in the atmosphere that react with the surface and either desorb glycine or break it up. The ablation process is studied as a function of entry speed and atmospheric composition. The AURORA code from the commercially available software package CHEMKIN is used in the study.

  12. Laser ablation of multilayer polymer films

    We study the efficiency of using multilayer structures as an etch-stop mechanism in the ablation of polyimide films by ultraviolet lasers. The study is done using a photothermal model that includes the light absorption by the decomposed fragments, which shield the polymer from the laser beam, an intermediate zone in which the polymer is suffering a phase transition and the underlying unburned material. The layers are differentiated from each other through their optical properties. Variation in the optical properties of polyimide has been achieved by a proper selection of impurities. From our modeling work, we conclude that optically thin foils may be used as etch stop in the ablation process when the penetration depth of the middle layer is around three times larger than the penetration depth of the surrounding layers, this for fluences below 200 mJ/cm2. We also present some experimental results

  13. Palliative Radiofrequency Ablation for Recurrent Prostate Cancer

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive local therapy for cancer. Its efficacy is now becoming well documented in many different organs, including liver, kidney, and lung. The goal of RFA is typically complete eradication of a tumor in lieu of an invasive surgical procedure. However, RFA can also play an important role in the palliative care of cancer patients. Tumors which are surgically unresectable and incompatible for complete ablation present the opportunity for RFA to be used in a new paradigm. Cancer pain runs the gamut from minor discomfort relieved with mild pain medication to unrelenting suffering for the patient, poorly controlled by conventional means. RFA is a tool which can potentially palliate intractable cancer pain. We present here a case in which RFA provided pain relief in a patient with metastatic prostate cancer with pain uncontrolled by conventional methods

  14. Radiofrequency thermal ablation of renal tumors.

    De Filippo, Massimo; Bozzetti, Francesca; Martora, Rosa; Zagaria, Raffaella; Ferretti, Stefania; Macarini, Luca; Brunese, Luca; Rotondo, Antonio; Rossi, Cristina

    2014-07-01

    Percutaneous radiofrequency ablation (PRFA) of renal malignancies is currently a therapeutic option for patients who are not able to undergo surgery. Some authors consider PRFA as the therapeutic standard in the treatment of renal neoplasms in non-operable patients due to comorbid conditions and in patients with mild-moderate renal failure, to preserve residual renal functionality. The use of PRFA has become more and more widespread due to a rise in the incidental detection of renal cell carcinomas with the ever-increasing use of Imaging for the study of abdominal diseases. Clinical studies indicate that RF ablation is an effective therapy with a low level of risk of complications, which provides good results in selected patients over short and medium term periods of time, however up to now few long-term studies have been carried out which can confirm the effectiveness of PRFA. PMID:25024061

  15. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

    Liu, Yu; Fite, Brett Z; Mahakian, Lisa M; Johnson, Sarah M; Larrat, Benoit; Dumont, Erik; Ferrara, Katherine W

    2015-01-01

    Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI) provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU) ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable. PMID:26439259

  16. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

    Yu Liu

    Full Text Available Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm, as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

  17. Radioiodine Remnant Ablation: A Critical Review

    Bal, Chandra Sekhar; Padhy, Ajit Kumar

    2015-01-01

    Radioiodine remnant ablation (RRA) is considered a safe and effective method for eliminating residual thyroid tissue, as well as microscopic disease if at all present in thyroid bed following thyroidectomy. The rationale of RRA is that in the absence of thyroid tissue, serum thyroglobulin (Tg) measurement can be used as an excellent tumor marker. Other considerations are like the presence of significant remnant thyroid tissue makes detection and treatment of nodal or distant metastases diffic...

  18. Ablating and charring of heat shield materials

    Rahimian, M.H.; Shabani, M.R. [Univ. of Tehran, Faculty of Engineering, Mechanical Engineering Dept., Tehran (Iran, Islamic Republic of)]. E-mail: rahimyan@ut.ac.ir; shubani@me.ut.ac.ir

    2003-07-01

    The objective of this research is to estimate ablating and charring of heat shield materials in severe aero thermal / erosive environments. This requires an accurate and rapid technique for its serious heat transfer with moving boundary. Aerodynamic heating is obtained by an explicit relation. Fully implicit method is used for heat transfer calculation. Moving boundary is captured by VOF method. Thickness of heat shield, temperature of moving surface and radiation heat is presented. The results are in good agreement with other calculations. (author)

  19. Ablating and charring of heat shield materials

    The objective of this research is to estimate ablating and charring of heat shield materials in severe aero thermal / erosive environments. This requires an accurate and rapid technique for its serious heat transfer with moving boundary. Aerodynamic heating is obtained by an explicit relation. Fully implicit method is used for heat transfer calculation. Moving boundary is captured by VOF method. Thickness of heat shield, temperature of moving surface and radiation heat is presented. The results are in good agreement with other calculations. (author)

  20. Design calculations for NIF convergent ablator experiments

    Olson R.E.

    2013-11-01

    Full Text Available The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash ρr, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.

  1. Design calculations for NIF convergent ablator experiments

    Olson R.E.; Hicks D.G.; Meezan N.B.; Callahan D.A.; Landen O.L.; Jones O.S.; Langer S.H.; Kline J.L.; Wilson D.C.; Rinderknecht H.; Zylstra A.; Petrasso R.D.

    2013-01-01

    The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash ρr, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.

  2. Resolving Bias in Laser Ablation Geochronology

    Bowring, James; Horstwood, Matthew; Gehrels, George

    2013-06-01

    Increasingly, scientific investigations requiring geochronology utilize laser ablation (LA)-inductively coupled plasma mass spectrometry (ICPMS), taking advantage of the efficiency and throughput possible for uranium-thorium-lead (U-Th-Pb) dating. A number of biases exist when comparing data among laboratories and an ongoing community-based effort is working to resolve and eliminate these biases to improve the accuracy of scientific interpretation based on these data.

  3. Electrolytic Effects During Tissue Ablation by Electroporation.

    Rubinsky, L; Guenther, E.; Mikus, P; Stehling, M; Rubinsky, B

    2015-01-01

    Nonthermal irreversible electroporation is a new tissue ablation technique that consists of applying pulsed electric fields across cells to induce cell death by creating permanent defects in the cell membrane. Nonthermal irreversible electroporation is of interest because it allows treatment near sensitive tissue structures such as blood vessels and nerves. Two recent articles report that electrolytic reaction products at electrodes can be combined with electroporation pulses to augment and o...

  4. Thermal properties of ablative phenolic resins

    Srebrenkoska, Vineta; Dimeski, Dimko; BOGOEVA-GACEVA, Gordana

    2002-01-01

    Phenolic resins are known for their excellent thermal properties and chemical stability and are widely used in automotive industry, electrical engineering, military industry and industry of construction materials. Their attractive properties have been especially exploited in high temperature applications. Recently a wide range of phenolic resins for different applications is available on the market. In this paper the properties of two types of ablative phenolic resins are compared: resin B...

  5. Generalized atomic displacements in crystallographie structure analysis

    An attempt is made to summarize both theoretical and experimental aspects of generalized atomic displacement parameters (ADP's) in crystalline matter. Generalized displacement parameters are used to describe the weakening of Bragg intensities via the anharmonic (static or thermal) Debye-Waller factor (DWF) and its real-space counterpart, the generalized atomic probability density function (p.d.f.). The lattice dynamical base of the harmonic and anharmonic thermal DWF is discussed. It is pointed out that the static DWF frequently contains higher-order terms. The mathematical case for an experimental determination of generalized ADP's is given. The most popular current formulations (one-particle potential and statistical approaches) are reviewed and their individual limitations are discussed. Likewise the demands put on the quality and extent of experimental data are assessed. Some aids to the interpretation of generalized ADP's established by crystallographic least-squares procedures are given and a Monte-Carlo method for the calculation of errors in p.d.f. maps is presented. Finally, some prospects for future work are outlined and a more frequent comparison of theoretical calculations and experimental determinations of generalized ADP's is advocated. (orig.)

  6. Fluorescence enhancement aided by metal ion displacement.

    Susini, Vanessa; Ienco, Andrea; Lucia Rossi, Veronica; Paolicchi, Aldo; Sanesi, Antonio

    2016-06-15

    Immunosensors are one of the most common platform used in clinical laboratories, in particular the class based on Enzyme Linked Fluorescent Assays (ELFA) takes advantage of the amplification step of the enzyme, usually the alkaline phosphatase, that catalyzes the hydrolysis of a fluorescent substrate leading it to fluoresce. Anyway, they suffer in sensitivity if compared to molecular diagnostic or more modern in vitro diagnostic devices. In our work, a simple and effective mechanism to enhance the fluorescent signal, and hence the sensitivity of the system, is presented. It is based on the metal ion displacement principle in which a second fluorophore, in our case Calcein Blue, quenched by a cobalt ion is add to the first one (4-MUP), and, in presence of inorganic phosphate, it will be progressively activated by the inorganic phosphate itself leading to the metal displacement. In this way Calcein Blue, newly free to fluoresce, contributes to global fluorescent signal generated by 4-MU. We have tested our proof of principle on a currently used immunoanalyzer, that is VIDAS® system (bioMérieux, Marcy l'Etoile, France) obtaining a fluorescence enhancement of about 50% for each concentration of hydrolyzed 4-MUP tested. PMID:26851581

  7. Precision optical displacement measurements using biphotons

    Lyons, Kevin; Pang, Shengshi; Kwiat, Paul G.; Jordan, Andrew N.

    2016-04-01

    We propose and examine the use of biphoton pairs, such as those created in parametric down-conversion or four-wave mixing, to enhance the precision and the resolution of measuring optical displacements by position-sensitive detection. We show that the precision of measuring a small optical beam displacement with this method can be significantly enhanced by the correlation between the two photons, given the same optical mode. The improvement is largest if the correlations between the photons are strong, and falls off as the biphoton correlation weakens. More surprisingly, we find that the smallest resolvable parameter of a simple split detector scales as the inverse of the number of biphotons for small biphoton number ("Heisenberg scaling"), because the Fisher information diverges as the parameter to be estimated decreases in value. One usually sees this scaling only for systems with many entangled degrees of freedom. We discuss the transition for the split-detection scheme to the standard quantum limit scaling for imperfect correlations as the biphoton number is increased. An analysis of an N -pixel detector is also given to investigate the benefit of using a higher resolution detector. The physical limit of these metrology schemes is determined by the uncertainty in the birth zone of the biphoton in the nonlinear crystal.

  8. KTP-532 laser ablation of urethral strictures

    Malloy, Terrence R.

    1991-07-01

    In 1988, the KTP-532 laser was used to ablate a series of benign urethral strictures. Rather than using a single incision, as in urethrotomy, strictures were treated with a 360$DEG contact photoradiation. Thirty-one males, average age 53.2 years, received 37 treatments. Six patients underwent a second laser treatment. Stricture etiology was commonly iatrogenic (32%), traumatic (16%), and post-gonococcal (10%). Stricture location included mainly bulbar (49%), membranous (20%), and penile (12%) areas. The surgical technique consisted of a circumferential ablation followed by foley catheter placement (mean 10 days). Follow-up on 29 of 31 patients ranged from 1 to 16 months (mean 9.7) Complete success occurred in 17 patients (59%) who had no further symptoms or instrumentation. Partial success was seen in 6 patients (20.5%) with symptoms but no stricture recurrence. Six patients (20.5%) failed therapy requiring additional surgery or regular dilatations. No complications were encountered. Although longer assessment is required, KTP-532 laser ablation of urethral strictures appears efficacious.

  9. A tubular electrode for radiofrequency ablation therapy

    Antunes, Carlos Lemos Lemos Lemos

    2012-07-06

    Purpose – Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to carcinomas. Besides its mechanical application, SEMS can be regarded as well as potential electrode for performing RF ablation therapy on the tumor. The purpose of this work is to perform numerical and experimental analyses in order to characterize the lesion volume induced in biological tissue using this kind of tubular electrode. Design/methodology/approach – Data concerning electrical conductivity and dimension of the damaged tissue after RF ablation procedure were obtained from ex vivo samples. Next, numerical models using 3D finite element method were obtained reassembling the conditions considered at experimentation setup and results were compared. Findings – Numerical and experimental results show that a regular volume of damaged tissue can be obtained considering this type of electrode. Also, results obtained from numerical simulation are close to those obtained by experimentation. Originality/value – SEMSs, commonly used as devices to minimize obstruction problems due to the growth of tumors, may still be considered as an active electrode for RF ablation procedures. A method considering this observation is presented in this paper. Also, numerical simulation can be regarded in this case as a tool for determining the lesion volume.

  10. Radiative Ablation of Disks Around Massive Stars

    Kee, N D

    2015-01-01

    Hot, massive stars (spectral types O and B) have extreme luminosities ($10^4 -10^6 L_\\odot$) that drive strong stellar winds through UV line-scattering. Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar...

  11. Osteoid Osteoma Treated with Radiofrequency Ablation

    Murat Çakar

    2015-01-01

    Full Text Available Purpose. Our aim is to evaluate the results of treatment with computed tomography (CT guided percutaneous radiofrequency ablation for osteoid osteomas which were localized in a difficult area for operation. Materials and Methods. Glenoid, distal tibia, humerus shaft, proximal humerus, and in third finger of the hand proximal phalanx were involved in one patient. Proximal femur was involved in three patients, distal femur was involved in three patients, and proximal tibia was involved in two patients. 9 males and 4 females were aged 4 to 34 years (mean age: 18.5 years. All patients had pain and were evaluated with X-rays, CT, bone scintigraphy, and MRI. In all patients, RF ablation was performed with local anesthesia. The lesion heated to 90°C for 6 minutes. Results. All of the patients achieved complete pain relief after ablation and were fully weight bearing without any support. In all patients, there was soft tissue edema after the procedure. During follow-up, all patients were free from the pain and there was no sign about the tumor. There was no other complication after the process. Conclusion. CT guided RFA is a minimally invasive, safe, and cost-effective treatment for osteoid osteoma placed in difficult area for surgery.

  12. Investigating Age Resolution in Laser Ablation Geochronology

    Horstwood, Matt; Kosler, Jan; Jackson, Simon; Pearson, Norman; Sylvester, Paul

    2009-02-01

    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; Vancouver, British Columbia, Canada, 12-13 July 2008; Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-thorium-lead (U-Th-Pb) dating is an increasingly popular approach for determining the age of mineral grains and the timing of geological events. The spatial resolution offered by this technique allows detailed investigations of complex igneous and metamorphic processes, and the speed of data capture allows vast amounts of information to be gathered rapidly. Laser ablation U-Th-Pb dating is therefore becoming an increasingly influential technique to the geochronology community, providing cost-effective and ready access to age data for laboratories and end users worldwide. However, complications in acquiring, processing, and interpreting data can lead to inaccurate age information entering the literature. With the numbers of practitioners expanding rapidly, the need to standardize approaches and resolve difficulties (particularly involving the subjectivity in processing laser ablation U-Th-Pb data) is becoming important.

  13. Transient Newton rings in dielectrics upon fs laser ablation

    Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Solis, Javier

    2014-01-01

    We report the appearance of transient Newton rings in dielectrics (sapphire and lead-oxide glass) during ablation with single fs laser pulses. Employing femtosecond microscopy with 800 nm excitation and 400 nm illumination, we observe a characteristic ring pattern that dynamically changes for increasing delay times between pump and probe pulse. Such transient Newton rings have been previously observed in metals and semiconductors at fluences above the ablation threshold and were related to optical interference of the probe beam reflected at the front surface of the ablating layer and at the interface of the non-ablating substrate. Yet, it had been generally assumed that this phenomenon cannot be (and has not been) observed in dielectrics due to the different ablation mechanism and optical properties of dielectrics. The fact that we are able to observe them has important consequences for the comprehension of the ablation mechanisms in dielectrics and provides a new method for investigating these mechanisms in ...

  14. Picosecond laser ablation for silicon micro fuel cell fabrication

    We have investigated laser ablation as a microfabrication approach to produce micro fuel cells (MFCs) in silicon. Picosecond pulses (15 ps) at a wavelength of 355 nm are used to make all of the MFC structures. To assess the benefits and drawbacks of laser ablation, reference cells have been produced by deep reactive ion etching (DRIE) using matching geometries. Ablated and etched cells have been evaluated and compared side by side. Our conclusion is that picosecond laser ablation is very well suited for MFC fabrication. The ablated cells match or excel DRIE-microfabricated cells in terms of current and power densities. Ablated MFCs achieved 47.6 mW cm−2 of power density and 121 mA cm−2 current density. (paper)

  15. New tumor ablation techniques for cancer treatment (microwave, electroporation)

    Since the introduction of radiofrequency ablation (RFA) for the treatment of liver tumors at the end of the 1990's, indications for local ablation techniques have been extended to other organs, in particular, the lungs, kidneys and bones. These techniques have also been improved, in particular to try and overcome the limitations of radiofrequency techniques, especially the significant decrease in complete ablation rates for tumors larger than 3 cm and tumors that are contiguous to vessels larger than 3 mm. Microwave ablation is a rapidly developing thermal ablation technique similar to RFA but with numerous differences. Electroporation, a non-thermal ablation technique with other possibilities, is in earlier stages of clinical development. (authors)

  16. Convergent ablation measurements of plastic ablators in gas-filled rugby hohlraums on OMEGA

    Casner, A.; Jalinaud, T.; Masse, L.; Galmiche, D.

    2015-10-01

    Indirect-drive implosions experiments were conducted on the Omega Laser Facility to test the performance of uniformly doped plastic ablators for Inertial Confinement Fusion. The first convergent ablation measurements in gas-filled rugby hohlraums are reported. Ignition relevant limb velocities in the range from 150 to 300 μm .n s-1 have been reached by varying the laser drive energy and the initial capsule aspect ratio. The measured capsule trajectory and implosion velocity are in good agreement with 2D integrated simulations and a zero-dimensional modeling of the implosions. We demonstrate experimentally the scaling law for the maximum implosion velocity predicted by the improved rocket model [Y. Saillard, Nucl. Fusion 46, 1017 (2006)] in the high-ablation regime case.

  17. Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation): A Review.

    Paiella, Salvatore; Salvia, Roberto; Ramera, Marco; Girelli, Roberto; Frigerio, Isabella; Giardino, Alessandro; Allegrini, Valentina; Bassi, Claudio

    2016-01-01

    Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC) accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA) and Irreversible Electroporation (IRE) are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on the use of these techniques have already demonstrated encouraging results in terms of safety and feasibility. Unfortunately, few studies on their efficacy are currently available. Even though some reports on the overall survival are encouraging, randomized studies are still required to corroborate these findings. This study provides an up-to-date overview and a thematic summary of the current available evidence on the application of RFA and IRE on PDAC, together with a comparison of the two procedures. PMID:26981115

  18. Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation: A Review

    Salvatore Paiella

    2016-01-01

    Full Text Available Pancreatic ductal adenocarcinoma (PDAC has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA and Irreversible Electroporation (IRE are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on the use of these techniques have already demonstrated encouraging results in terms of safety and feasibility. Unfortunately, few studies on their efficacy are currently available. Even though some reports on the overall survival are encouraging, randomized studies are still required to corroborate these findings. This study provides an up-to-date overview and a thematic summary of the current available evidence on the application of RFA and IRE on PDAC, together with a comparison of the two procedures.

  19. Pulse tube stirling machine with warm gas-driven displacer

    Zhu, Shaowei; Nogawa, Masafumi

    2010-05-01

    A pulse tube type stirling machine with warm gas-driven displacer which has a displacer rod is discussed with numerical simulation when it is used as a cryogenic refrigerator, room temperature refrigerator and engine. It has both the advantages of gas-driven-stirling machine with high efficiency and simplicity and the advantages of pulse tube machine with no moving parts at low temperatures. A nodal analysis method that includes the linear motor and the displacer in the machine is introduced. Numerical results show that it has high potential to be used as the cryogenic refrigerator, room temperature refrigerator and engine. In this type of machine, there is an optimum phase angle between displacer and piston, and an optimum swept volume ratio of displacer over compressor for efficiency. The phase angle and swept volume ratio can be adjusted by the natural frequency of the displacer and the diameter of the displacer rod when it is used as a refrigerator.

  20. The effect of base pair mismatch on DNA strand displacement

    Broadwater, Bo

    2016-01-01

    DNA strand displacement is a key reaction in DNA homologous recombination and DNA mismatch repair and is also heavily utilized in DNA-based computation and locomotion. Despite its ubiquity in science and engineering, sequence-dependent effects of displacement kinetics have not been extensively characterized. Here, we measured toehold-mediated strand displacement kinetics using single-molecule fluorescence in the presence of a single base pair mismatch. The apparent displacement rate varied significantly when the mismatch was introduced in the invading DNA strand. The rate generally decreased as the mismatch in the invader was encountered earlier in displacement. Our data indicate that a single base pair mismatch in the invader stalls branch migration, and displacement occurs via direct dissociation of the destabilized incumbent strand from the substrate strand. We combined both branch migration and direct dissociation into a model, which we term, the concurrent displacement model, and used the first passage t...

  1. Role of Remote Navigation Systems in AF Ablation

    Boris Schmidt, MD

    2011-02-01

    Full Text Available During the past decade atrial fibrillation (AF ablation has developed from being an experimental treatment option to an evidence based therapy implemented in current guidelines.1-2 Irrigated radiofrequency current guided ablations remain the golden standard of pulmonary vein isolation (PVI procedures. Although practiced more frequently, it remains a demanding procedure requiring skilful operators. Novel technologies such as balloon based catheters or remote navigation (RN systems have been developed to overcome the pitfalls of manual ablation procedures.

  2. Cooled Radiofrequency Ablation for Bilateral Greater Occipital Neuralgia

    Tiffany Vu; Akhil Chhatre

    2014-01-01

    This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the subocci...

  3. Radiofrequency Ablation of Thyroid Nodules: Basic Principles and Clinical Application

    Ji Hoon Shin; Jung Hwan Baek; Eun Ju Ha; Jeong Hyun Lee

    2012-01-01

    Radiofrequency (RF) ablation has been gaining popularity as a minimally invasive treatment for benign thyroid nodules regardless of the extent of the solid component. RF ablation of benign nodules demonstrated volume reductions of 33–58% after one month and 51–85% after six months, while solving nodule-related clinical problems. RF ablation has recently shown positive short-term results for locoregional control as well as symptom improvement in patients with recurrent thyroid cancers. This pa...

  4. Numerical simulation of copper ablation by ultrashort laser pulses

    Ding, PengJi; Hu, BiTao; Li, Yuhong

    2011-01-01

    Using a modified self-consistent one-dimensional hydrodynamic lagrangian fluid code, laser ablation of solid copper by ultrashort laser pulses in vacuum was simulated to study fundamental mechanisms and to provide a guide for drilling periodic microholes or microgratings on the metal surface. The simulated laser ablation threshold is a approximate constancy in femtosecond regime and increases as the square root of pulse duration in picosecond regime. The ablation depth as a function of pulse ...

  5. Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms

    Milasinovic, Slobodan; Liu, Yaoming; Gasper, Gerald L.; Zhao, Youbo; Johnston, Joanna L.; Gordon, Robert J.; Hanley, Luke

    2010-01-01

    Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100 fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionizat...

  6. RECENT ADVANCES IN PULSED LASER ABLATED PLASMA PLUMES: A REVIEW

    ASHUTOSH DWIVEDI

    2007-01-01

    Pulsed laser ablation is a process in which an intense laser pulse interacts with the matter producing plasma. The present work describes the theoretical work being conducted in the past for the pulsed laser ablation phenomenon. It incorporates the theoretical models being proposed by various researchers around the globe for pulsed laser ablation. The main processes involved in the laser–matter interaction leading to plasma plume formation are the absorption and the reflection of the incident...

  7. Neuropsychological Decline After Catheter Ablation of Atrial Fibrillation

    Schwarz, N

    2011-09-01

    Full Text Available The article “Neuropsychological decline after cath- eter ablation of atrial fibrillation” by Schwarz et al. is the first publication that focused on cognitive side effects of elective circumferential pulmonary vein isolation (PVI.1 Adverse neuropsychological changes after left atrial catheter ablation, as report- ed in this paper, were found in verbal memory and the result, conjoined with ischemic brain lesions, might represent cerebral side-effects of the ablation procedure.

  8. Efficiency of ablative plasma energy transfer into a massive aluminum target using different atomic number ablators

    Kasperczuk, A.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Stepniewski, W.; Jach, K.; Swierczynski, R.; Renner, Oldřich; Šmíd, Michal; Ullschmied, Jiří; Cikhart, J.; Klír, D.; Kubeš, P.; Řezáč, K.; Krouský, Eduard; Pfeifer, Miroslav; Skála, Jiří

    2015-01-01

    Roč. 33, č. 3 (2015), s. 379-386. ISSN 0263-0346 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk(CZ) LD14089 EU Projects: European Commission(XE) 284464 - LASERLAB-EUROPE Grant ostatní: ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; AVČR(CZ) M100101208 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : ablator atomic number * crater volume * laser energy transfer * plasma ablative pressure Subject RIV: BL - Plasma and Gas Discharge Physics; BH - Optics, Masers, Lasers (UFP-V) Impact factor: 1.295, year: 2014

  9. The Role of Intracardiac Echocardiography in Atrial Fibrillation Ablation

    Elad Anter, MD

    2009-10-01

    Full Text Available Radiofrequency catheter ablation of pulmonary veins has emerged as an effective therapy for patients with symptomatic atrial fibrillation. Advances in real-time intracardiac echocardiography with 2D and Doppler color flow imaging have led to it integration in atrial fibrillation ablation procedures. It allows imaging of the left atrium and pulmonary veins, including identification of anatomic variations. It has an important role in guiding transseptal catheterization, imaging the pulmonary vein ostia, assisting in accurate placement of mapping and ablation catheters, monitoring lesion morphology and flow changes in the ablated pulmonary veins, hence allowing titration of energy delivery. Importantly, it allows instant detection of procedural complications.

  10. Numerical modeling of ultrashort-pulse laser ablation of silicon

    Silicon ablation by a single ultrashort laser pulse is simulated through a computer model. The agreement between results obtained through the model and experimental data found in the literature supports the hypothesis made by the authors in considering thermal evaporation as the dominant ablation mechanism in silicon. Two distinctive thresholds are defined for the ablation procedure leading to a better interpretation of experimental data. The dependence of ablation fluence thresholds on both wavelength and pulse width is discussed. An approximate analytical model describing the crater formation process is proposed and indicative results are presented.

  11. Radiofrequency Ablation of Thyroid Nodules: Basic Principles and Clinical Application

    Ji Hoon Shin

    2012-01-01

    Full Text Available Radiofrequency (RF ablation has been gaining popularity as a minimally invasive treatment for benign thyroid nodules regardless of the extent of the solid component. RF ablation of benign nodules demonstrated volume reductions of 33–58% after one month and 51–85% after six months, while solving nodule-related clinical problems. RF ablation has recently shown positive short-term results for locoregional control as well as symptom improvement in patients with recurrent thyroid cancers. This paper reviews the basic physics, indications, patient preparation, devices, procedures, clinical results, and complications of RF ablation.

  12. CT-guided radiofrequency tumor ablation in children

    Botsa, Evanthia [National and Kapodistrian University of Athens, First Pediatric Clinic, Agia Sofia Children' s Hospital, Athens (Greece); Poulou, Loukia S.; Koundouraki, Antonia; Thanos, Loukas [Sotiria General Hospital for Chest Diseases, Department of Medical Imaging and Interventional Radiology, Athens (Greece); Koutsogiannis, Ioannis [General Military Hospital NIMTS, Department of Medical Imaging, Athens (Greece); Ziakas, Panayiotis D. [Warren Alpert Medical School of Brown University Rhode Island Hospital, Division of Infectious Diseases, Providence, RI (United States); Alexopoulou, Efthimia [Attikon University Hospital, Second Department of Radiology, Athens University School of Medicine, Athens (Greece)

    2014-11-15

    Image-guided radiofrequency ablation is a well-accepted technique of interventional oncology in adults. To evaluate the efficacy and safety of CT-guided radiofrequency ablation as a minimally invasive treatment for metastatic neoplasms in children. A total of 15 radiofrequency ablation sessions were performed in 12 children and young adults (median age 9.5; range 5-18 years) with metastatic malignancies. Seven children and young adults had secondary hepatic lesions, three had pulmonary and two had bone lesions. Radiofrequency ablation was performed under conscious sedation. The median lesion size was 1.7 cm (range 1.3-2.8 cm). The median time for ablation was 8 min (range 7-10 min). Radiofrequency procedures were technically successful in all tumors. Postablation imaging immediately after, and 1 month and 3 months after radiofrequency ablation showed total necrosis in all patients. At 6-month follow-up, three patients (all with lesion size >2 cm) had local recurrence and underwent a second radiofrequency ablation session. At 2-year follow-up no patient had recurrence of the treated tumor. Post-ablation syndrome occurred in four children. No major complication occurred. CT-guided radiofrequency tumor ablation was safe and efficient for palliative treatment in our cohort of patients. (orig.)

  13. Development of laser ablation plasma by anisotropic self-radiation

    Ohnishi Naofumi

    2013-11-01

    Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.

  14. Thermal character in organic polymers with nanojoule femtosecond laser ablation

    Xiaochang Ni(倪晓昌); Ching-Yue Wang(王清月); Yanfeng Li(栗岩峰); Minglie Hu(胡明列); Zhuan Wang(王专); Lu Chai(柴路)

    2003-01-01

    Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diameters of the dots ablated in the organic polymers are influenced by the laser fluence and the number of laser pulses. It is observed that heat is diffused in a threadlike manner in all directions around the central focus region. Explanations of the observed phenomena are presented. A one-dimensional waveguide is also ablated in the organic polymers.

  15. Laser ablation loading of a surface-electrode ion trap

    Leibrandt, David R.; Clark, Robert J.; Labaziewicz, Jaroslaw; Antohi, Paul; Bakr, Waseem; Brown, Kenneth R.; Chuang, Isaac L.

    2007-01-01

    We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Addi...

  16. High resolution patterning of sapphire by F2-laser ablation

    Wiesner, Markus; Ihlemann, Jürgen

    2011-01-01

    The ablation behavior of single crystalline sapphire with nanosecond laser pulses at 157 nm wavelength is investigated. Ablation rates of about 10 to 100 nm/pulse are obtained at fluences ranging from 1 to 9 J/cm2. At moderate fluences, incubation behavior is observed, i.e. ablation starts after material modification by a number of laser pulses. The ablation can be utilized to fabricate sapphire micro-optics. The capability of creating lenses or gratings on the tip of sapphire fibers is demon...

  17. The Role of Intracardiac Echocardiography in Atrial Fibrillation Ablation

    Elad Anter

    2009-10-01

    Full Text Available Radiofrequency catheter ablation of pulmonary veins has emerged as an effective therapy for patients with symptomatic atrial fibrillation. Advances in real-time intracardiac echocardiography with 2D and Doppler color flow imaging have led to its integration in atrial fibrillation ablation procedures. It allows imaging of the left atrium and pulmonary veins, including identification of anatomic variations. It has an important role in guiding transseptal catheterization, imaging the pulmonary vein ostia, assisting in accurate placement of mapping and ablation catheters, monitoring lesion morphology and flow changes in the ablated pulmonary veins, hence allowing titration of energy delivery. Importantly, it allows instant detection of procedural complications.

  18. Analog Computation by DNA Strand Displacement Circuits.

    Song, Tianqi; Garg, Sudhanshu; Mokhtar, Reem; Bui, Hieu; Reif, John

    2016-08-19

    DNA circuits have been widely used to develop biological computing devices because of their high programmability and versatility. Here, we propose an architecture for the systematic construction of DNA circuits for analog computation based on DNA strand displacement. The elementary gates in our architecture include addition, subtraction, and multiplication gates. The input and output of these gates are analog, which means that they are directly represented by the concentrations of the input and output DNA strands, respectively, without requiring a threshold for converting to Boolean signals. We provide detailed domain designs and kinetic simulations of the gates to demonstrate their expected performance. On the basis of these gates, we describe how DNA circuits to compute polynomial functions of inputs can be built. Using Taylor Series and Newton Iteration methods, functions beyond the scope of polynomials can also be computed by DNA circuits built upon our architecture. PMID:27363950

  19. Axial flow positive displacement worm compressor

    Murrow, Kurt David (Inventor); Giffin, Rollin George (Inventor); Fakunle, Oladapo (Inventor)

    2010-01-01

    An axial flow positive displacement compressor has an inlet axially spaced apart and upstream from an outlet. Inner and outer bodies have offset inner and outer axes extend from the inlet to the outlet through first and second sections of a compressor assembly in serial downstream flow relationship. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes respectively. The inner and outer helical blades extend radially outwardly and inwardly respectively. The helical blades have first and second twist slopes in the first and second sections respectively. The first twist slopes are less than the second twist slopes. An engine including the compressor has in downstream serial flow relationship from the compressor a combustor and a high pressure turbine drivingly connected to the compressor by a high pressure shaft.

  20. Personal Exposure in Displacement Ventilated Rooms

    Brohus, Henrik; Nielsen, Peter Vilhelm

    1996-01-01

    Personal exposure in a displacement ventilated room is examined. The stratified flow and the considerable concentration gradients necessitate an improvement of the widely used fully mixing compartmental approach. The exposure of a seated and a standing person in proportion to the stratification...... height is examined by means of full-scale measurements. A breathing thermal manikin is used to simulate a person. It is found that the flow in the boundary layer around a person is able to a great extent to entrain and transport air from below the breathing zone. In the case of non-passive, heated...... contaminant sources, this entrainment improves the indoor air quality. Measurements of exposure due to a passive contaminant source show a significant dependence on the flow field as well as on the contaminant source location. Poor system performance is found in the case of a passive contaminant released in...

  1. Displaced fracture through the anterior atlantal synchondrosis

    Thakar, Chrishan; Allibone, James [Royal National Orthopaedic Hospital NHS Trust, Department of Spinal Deformity, Stanmore, Middlesex (United Kingdom); Harish, Srinivasan [Royal National Orthopaedic Hospital NHS Trust, Department of Radiology, Stanmore, Middlesex (United Kingdom); Saifuddin, Asif [Royal National Orthopaedic Hospital NHS Trust, Department of Radiology, Stanmore, Middlesex (United Kingdom); University College, The Institute of Orthopaedics and Musculoskeletal Sciences, London (United Kingdom)

    2005-09-01

    In the acute setting, accurate radiological interpretation of paediatric cervical spine trauma can be difficult due to a combination of normal variants and presence of multiple synchondroses. We present a rare case of a fracture through the anterior atlantal synchondrosis in a paediatric spine. A five-year-old boy, who fell backwards onto the top of his head while swinging across on a monkey bar frame, presented with neck pain, cervical muscle spasm and decreased right lateral rotation and extension of his neck. Computed tomography showed a displaced diastatic fracture through right anterior atlantal synchondrosis. There are only 12 cases of paediatric C1 fractures reported in the world literature. The importance of considering this diagnosis in the appropriate clinical setting, and the normal variants in the paediatric atlas that can cause diagnostic dilemma to the interpreting radiologist, are discussed in this case report. (orig.)

  2. Micromachined Tunneling Displacement Transducers for Physical Sensors

    Kenny, T. W.; Kaiser, W. J.; Podosek, J. A.; Rockstad, H. K.; Reynolds, J. K.; Vote, E. C.

    1993-01-01

    We have designed and constructed a series of tunneling sensors which take advantage of the extreme position sensitivity of electron tunneling. In these sensors, a tunneling displacement transducer, based on scanning tunneling microscopy principles, is used to detect the signal-induced motion of a sensor element. Through the use of high-resonant frequency mechanical elements for the transducer, sensors may be constructed which offer wide bandwidth, and are robust and easily operated. Silicon micromachining may be used to fabricate the transducer elements, allowing integration of sensor and control electronics. Examples of tunneling accelerometers and infrared detectors will be discussed. In each case, the use of the tunneling transducer allows miniaturization of the sensor as well as enhancement of the sensor performance.

  3. Relativistic Lagrangian displacement field and tensor perturbations

    Rampf, Cornelius

    2014-01-01

    We investigate the purely spatial Lagrangian coordinate transformation from the Lagrangian to the fundamental Eulerian frame. We demonstrate three techniques for extracting the relativistic displacement field from a given solution in the Lagrangian frame. These techniques are (a) from defining a local set of Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a specific gauge transformation; and (c) from a fully non-perturbative approach based on the ADM split. The latter approach shows that this decomposition is not tied to a specific perturbative formulation for the solution of the Einstein equations. Rather, it can be defined at the level of the non-perturbative coordinate change from the Lagrangian to the Eulerian description. Studying such different techniques is useful because it allows us to compare and develop further the various approximation techniques available in the Lagrangian formulation. We find that one has to solve for gravitational waves in the relativistic analysis,...

  4. Superconducting inductive displacement detection of a microcantilever

    Vinante, A., E-mail: anvinante@fbk.eu [Istituto di Fotonica e Nanotecnologie, CNR - Fondazione Bruno Kessler, I-38123 Povo, Trento (Italy)

    2014-07-21

    We demonstrate a superconducting inductive technique to measure the displacement of a micromechanical resonator. In our scheme, a type I superconducting microsphere is attached to the free end of a microcantilever and approached to the loop of a dc Superconducting Quantum Interference Device (SQUID) microsusceptometer. A local magnetic field as low as 100 μT, generated by a field coil concentric to the SQUID, enables detection of the cantilever thermomechanical noise at 4.2 K. The magnetomechanical coupling and the magnetic spring are in good agreement with image method calculations assuming pure Meissner effect. These measurements are relevant to recent proposals of quantum magnetomechanics experiments based on levitating superconducting microparticles.

  5. Searching for displaced Higgs boson decays

    Csáki, Csaba; Kuflik, Eric; Lombardo, Salvator; Slone, Oren

    2015-10-01

    We study a simplified model of the Standard Model (SM) Higgs boson decaying to a degenerate pair of scalars which travel a macroscopic distance before decaying to SM particles. This is the leading signal for many well-motivated solutions to the hierarchy problem that do not propose additional light colored particles. Bounds for displaced Higgs boson decays below 10 cm are found by recasting existing tracker searches from Run I. New tracker search strategies, sensitive to the characteristics of these models and similar decays, are proposed with sensitivities projected for Run II at √{s }=13 TeV . With 20 fb-1 of data, we find that Higgs branching ratios down to 2 ×1 0-4 can be probed for centimeter decay lengths.

  6. Intrinsic mean-square displacements in proteins

    Vural, Derya; Glyde, Henry R.

    2012-07-01

    The thermal mean-square displacement (MSD) of hydrogen in proteins and its associated hydration water is measured by neutron scattering experiments and used an indicator of protein function. The observed MSD as currently determined depends on the energy resolution width of the neutron scattering instrument employed. We propose a method for obtaining the intrinsic MSD of H in the proteins, one that is independent of the instrument resolution width. The intrinsic MSD is defined as the infinite time value of that appears in the Debye-Waller factor. The method consists of fitting a model to the resolution broadened elastic incoherent structure factor or to the resolution dependent MSD. The model contains the intrinsic MSD, the instrument resolution width, and a rate constant characterizing the motions of H in the protein. The method is illustrated by obtaining the intrinsic MSD of heparan sulphate (HS-0.4), ribonuclease A, and staphysloccal nuclase (SNase) from data in the literature.

  7. Intrinsic Mean Square Displacements in Proteins

    Vural, Derya

    2012-01-01

    The thermal mean square displacement (MSD) of hydrogen in proteins and its associated hydration water is measured by neutron scattering experiments and used an indicator of protein function. The observed MSD as currently determined depends on the energy resolution width of the neutron scattering instrument employed. We propose a method for obtaining the intrinsic MSD of H in the proteins, one that is independent of the instrument resolution width. The intrinsic MSD is defined as the infinite time value of that appears in the Debye-Waller factor. The method consists of fitting a model to the resolution broadened elastic incoherent structure factor or to the resolution dependent MSD. The model contains the intrinsic MSD, the instrument resolution width and a rate constant characterizing the motions of H in the protein. The method is illustrated by obtaining the intrinsic MSD of heparan sulphate (HS-0.4), Ribonuclease A and Staphysloccal Nuclase (SNase) from data in the literature.

  8. Artificial Neural Network for Displacement Vectors Determination

    P. Bohmann

    1997-09-01

    Full Text Available An artificial neural network (NN for displacement vectors (DV determination is presented in this paper. DV are computed in areas which are essential for image analysis and computer vision, in areas where are edges, lines, corners etc. These special features are found by edges operators with the following filtration. The filtration is performed by a threshold function. The next step is DV computation by 2D Hamming artificial neural network. A method of DV computation is based on the full search block matching algorithms. The pre-processing (edges finding is the reason why the correlation function is very simple, the process of DV determination needs less computation and the structure of the NN is simpler.

  9. Relativistic Lagrangian displacement field and tensor perturbations

    Rampf, Cornelius; Wiegand, Alexander

    2014-12-01

    We investigate the purely spatial Lagrangian coordinate transformation from the Lagrangian to the basic Eulerian frame. We demonstrate three techniques for extracting the relativistic displacement field from a given solution in the Lagrangian frame. These techniques are (a) from defining a local set of Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a specific gauge transformation; and (c) from a fully nonperturbative approach based on the Arnowitt-Deser-Misner (ADM) split. The latter approach shows that this decomposition is not tied to a specific perturbative formulation for the solution of the Einstein equations. Rather, it can be defined at the level of the nonperturbative coordinate change from the Lagrangian to the Eulerian description. Studying such different techniques is useful because it allows us to compare and develop further the various approximation techniques available in the Lagrangian formulation. We find that one has to solve the gravitational wave equation in the relativistic analysis, otherwise the corresponding Newtonian limit will necessarily contain spurious nonpropagating tensor artifacts at second order in the Eulerian frame. We also derive the magnetic part of the Weyl tensor in the Lagrangian frame, and find that it is not only excited by gravitational waves but also by tensor perturbations which are induced through the nonlinear frame dragging. We apply our findings to calculate for the first time the relativistic displacement field, up to second order, for a Λ CDM Universe in the presence of a local primordial non-Gaussian component. Finally, we also comment on recent claims about whether mass conservation in the Lagrangian frame is violated.

  10. Systematic review of mini-implant displacement under orthodontic loading

    Manuel Nienkemper; Jörg Handschel; Dieter Drescher

    2014-01-01

    A growing number of studies have reported that mini-implants do not remain in exactly the same position during treatment, although they remain stable. The aim of this review was to collect data regarding primary displacement immediately straight after loading and secondary displacement over time. A systematic review was performed to investigate primary and secondary displacement. The amount and type of displacement were recorded. A total of 27 studies were included. Sixteen in vitro studies or studies using finite element analysis addressed primary displacement, and nine clinical studies and two animal studies addressed secondary displacement. Significant primary displacement was detected (6.4-24.4 mm) for relevant orthodontic forces (0.5-2.5 N). The mean secondary displacement ranged from 0 to 2.7 mm for entire mini-implants. The maximum values for each clinical study ranged from 1.0 to 4.1 mm for the head, 1.0 to 1.5 for the body and 1.0 to 1.92 mm for the tail part. The most frequent type of movement was controlled tipping or bodily movement. Primary displacement did not reach a clinically significant level. However, clinicians can expect relevant secondary displacement in the direction of force. Consequently, decentralized insertion within the inter-radicular space, away from force direction, might be favourable. More evidence is needed to provide quantitative recommendations.

  11. CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results

    Purpose. This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. Methods. We included 22 consecutive patients (3 women; age 74.2 ± 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 ± 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Results. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 ± 13.6 min and 43.7 ± 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 ± 8.8 months, local recurrence-free survival was 14.4 ± 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 ± 16.6 ml/min/1.73 m2 before RF ablation vs. 47.2 ± 11.9 ml/min/1.73 m2 after RF ablation; not significant). Conclusions. CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

  12. Near-IR imaging of Erbium Laser Ablation with a Water Spray

    Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

    2008-01-01

    Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium la...

  13. Mechanism study of skin tissue ablation by nanosecond laser pulses

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  14. Metal particles produced by laser ablation for ICP-MSmeasurements

    Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

  15. Electroporation ablation: A new energy modality for ablation of arrhythmogenic cardiac substrate

    van Driel, VJHM

    2016-01-01

    At the very end of the Direct Current (DC) era, low-energy DC ablation was demonstrated to cause myocardial lesions by non-thermal irreversible electroporation (IRE) (permanent formation of pores in the cell membrane, leading to cell death), without arcing and/or barotrauma. To eliminate rather smal

  16. Radio-frequency ablation helps preserve nephrons in salvage of failed microwave ablation for a renal cancer in a solitary kidney

    Castle, Scott M.; Nelson Salas; Leveillee, Raymond J.

    2013-01-01

    Recurrent tumors after renal ablative therapy present a challenge for clinicians. New ablative modalities, including microwave ablation (MWA), have very limited experience in methods of retreating ablation failures. Additionally, in MWA, no long-term outcomes have been reported. In patients having local tumor recurrence, options for surveillance or surgical salvage must be assessed. We present a case to help assess radio-frequency ablation (RFA) for salvage of failed MWA. We report a 63-year-...

  17. Thermal Performance of Ablative/ Ceramic Composite

    Adriana STEFAN

    2014-12-01

    Full Text Available A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM and Ceramic Matrix Composite (CMC material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C, at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar conditions. The average weigh loss was calculated for all the samples from one set, without differentiating the adhesive used as the weight loss is due to the ablative material consumption that is the same in all the samples and is up to 2%. The thermal shock test proves that, thermally, all joints behaved similarly, the two parts withstanding the test successfully and the assembly maintaining its integrity.

  18. On Virtual Displacement and Virtual Work in Lagrangian Dynamics

    Ray, S; Ray, Subhankar

    2006-01-01

    The confusion and ambiguity encountered by students, in understanding virtual displacement and virtual work, is discussed in this article. A definition of virtual displacement is presented that allows one to express them explicitly for holonomic (velocity independent), non-holonomic (velocity dependent), scleronomous (time independent) and rheonomous (time dependent) constraints. It is observed that for holonomic, scleronomous constraints, the virtual displacements are the displacements allowed by the constraints. However, this is not so for a general class of constraints. For simple physical systems, it is shown that, the work done by the constraint forces on virtual displacements is zero. This motivates Lagrange's extension of d'Alembert's principle to system of particles in constrained motion. However a similar zero work principle does not hold for the allowed displacements. It is also demonstrated that d'Alembert's principle of zero virtual work is necessary for the solvability of a constrained mechanical...

  19. Reduce proton energy spread by target ablation

    Zhao, Shuan; Chen, Jiaer; Yan, Xueqing

    2015-01-01

    It's shown that, with strong target ablation monoenergetic protons along the laser direction is available during the laser aluminum foil interaction, which is different from the classic TNSA theory. When the laser pre-pulse is too strong that the whole target is vaporized, the energetic electrons generated in the gas preplasma will play an important role for the ion acceleration because the sheath field will not be available. These electrons beam, which is highly directional, will setup triangle envelope acceleration field along the laser direction at the target rear, reducing the ion energy spread.

  20. Ablation of polymers by ultraviolet pulsed laser

    The surface modifications of different polymers treated by far UV-Excimer laser (λ = 193mn, 248, 308nm) are analysed by X-Ray Photoelectrons Spectroscopy. The main feature observed depends strongly on the absorption coefficients. For the high absorbing polymers such (PVC, PS, PI,...) the mechanism of the UV-Excimer Laser interaction appears to be governed by an ablative photodecomposition process (APD) with an APD threshold. In the other limit, i.e. low absorbing polymer the interaction leads to a photothermal process. (author). 51 refs, 24 figs, 7 tabs

  1. Laser systems for ablative fractional resurfacing

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    of a variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional...... ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities...

  2. Obtention of Ti nanoparticles by laser ablation

    The obtention of Ti nanoparticles around 5-30 nm diameter through the laser ablation technique is reported. The formation of nanoparticles is carried out in He atmosphere to different pressures, placing directly in Si substrates (100) and in Cu grids. The results show that the work pressure is an important parameter that allows to control the nanoparticles size. Also the plasma characterization results are presented where the Ti II is the predominant specie with an average kinetic energy of 1824 eV. (Author)

  3. Ablation Plume Induced by Laser Euv Radiation

    Frolov, Oleksandr; Koláček, Karel; Schmidt, Jiří; Štraus, Jaroslav

    Dordrecht: Springer International Publishing, 2015 - (Rocca, J.; Menoni, C.; Marconi, M.), s. 397-403. (Springer Proceedings in Physics. 169). ISBN 978-3-319-19521-6. [International Conference on X-Ray Laser s/14./. Fort Collins, Colorado (US), 26.05.2014-30.05.2014] R&D Projects: GA ČR(CZ) GA14-29772S; GA MŠk(CZ) LG13029 Institutional support: RVO:61389021 Keywords : EUV laser * laser ablation * plume * Au * Al * Si * Cu * energy measurements Subject RIV: BL - Plasma and Gas Discharge Physics http://link.springer.com/chapter/10.1007/978-3-319-19521-6_52

  4. Resonant laser ablation: mechanisms and applications

    Resonant laser ablation (RLA) typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one or two photon resonant transition in the analyte of interest. This paper shows that RLA is well suited for highly sensitive analyses of complex samples. The examples actually studied are trace components in rhenium and technetium in nickel. The authors also studied the 2+1 multiphoton ionization spectrum of iron-56 detected by RLA of Re containing 70 ppm iron. Two-photon transition rates for Fe transitions were calculated perturbatively and found to agree semi-quantitatively with experimentally observed intensities. 17 refs., 3 figs

  5. Foil-strain-gauge-based displacement transducers and calibration device for displacement transducers

    Materials testing performed on various specimen materials with different techniques often reveal measuring method problems which cannot be solved by using commercial devices which are either too expensive or else are non-existent altogether. The institute remedied this situation by developing a number of laboratory devices of their own make two of which, i.e. a special displacement transducer and a device for the calibration and characteristics determination of transducers, are demonstrated in this report. (orig./HP)

  6. Displacement desorption test of coalbed methane and its mechanism exploring

    ZHANG Suian; HUO Yongzhong; YE Jianping; TANG Shuheng; MA Dongmin

    2005-01-01

    Through the test of CH4 displaced by CO2 using the coal sample as the adsorbent, this paper has found the coalbed methane (CBM) displacement desorption phenomenon under the natural conditions and CBM mining conditions. With the help of the adsorption theory of the modern physical chemistry and interfacial chemistry, the CBM competitive adsorption and displacement desorption mechanism are intensively discussed, and a new path for studying the CBM desorption mechanism in the CBM exploitation process is explored.

  7. Quantum Phonon Optics: Coherent and Squeezed Atomic Displacements

    Hu, X; Nori, Franco

    1996-01-01

    In this paper we investigate coherent and squeezed quantum states of phonons. The latter allow the possibility of modulating the quantum fluctuations of atomic displacements below the zero-point quantum noise level of coherent states. The expectation values and quantum fluctuations of both the atomic displacement and the lattice amplitude operators are calculated in these states---in some cases analytically. We also study the possibility of squeezing quantum noise in the atomic displacement u...

  8. Collective Displacement of Modular Robots Using Self-Reconfiguration

    Elian, Carrillo; Duhaut, Dominique

    2007-01-01

    Bioinspiration and Robotics Walking and Climbing Robots, Book edited by: Maki K. Habib , ISBN: 978-3-902613-15-8, Publisher: I-Tech Education and Publishing, Austria, Collective displacement is a very useful behaviour for living creatures. This behaviour can appear in a flock of birds, a school of fish, or a swarm of insects. Flocking behaviour is a common demonstration of the power of simple rules in collective displacement emergence by (Reynolds, 2007). The study of the displacement of a...

  9. A homogeneous nucleic acid hybridization assay based on strand displacement.

    Vary, C P

    1987-01-01

    A homogeneous nucleic acid hybridization assay which is conducted in solution and requires no separation steps is described. The assay is based on the concept of strand displacement. In the strand displacement assay, an RNA "signal strand" is hybridized within a larger DNA strand termed the "probe strand", which is, in turn, complementary to the target nucleic acid of interest. Hybridization of the target nucleic acid with the probe strand ultimately results in displacement of the RNA signal ...

  10. Control of DNA Strand Displacement Kinetics Using Toehold Exchange

    Zhang, David Yu; Winfree, Erik

    2009-01-01

    DNA is increasingly being used as the engineering material of choice for the construction of nanoscale circuits, structures, and motors. Many of these enzyme-free constructions function by DNA strand displacement reactions. The kinetics of strand displacement can be modulated by toeholds, short single-stranded segments of DNA that colocalize reactant DNA molecules. Recently, the toehold exchange process was introduced as a method for designing fast and reversible strand displacement reactions...

  11. Cleaning and Dewatering Fine Coal using Hydrophobic Displacement

    Smith, Kara E.

    2008-01-01

    A new processing technique, known as hydrophobic displacement, was explored as a means of simultaneously removing both mineral matter and surface moisture from coal in a single process. Previous thermodynamic analysis suggests that coal moisture will be spontaneously displaced by any oil with a contact angle greater than ninety degrees in water. Based on these results, six methods of hydrophobic displacement were evaluated: hand shaking, screening, air classification, centrifugation, filtra...

  12. A Wireless Laser Displacement Sensor Node for Structural Health Monitoring

    Se Woon Choi; Yousok Kim; Jong Moon Kim; Hyo Seon Park

    2013-01-01

    This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is enabled by a sensor node that consists of a sensor module, a code division multiple access (CDMA) communication module, a processor, and a power module. An LDS with a long measurement distanc...

  13. Time-dependent Displaced and Squeezed Number States

    Kim, S P

    2004-01-01

    We generalize the wave functions of the displaced and squeezed number states, found by Nieto, to a time-dependent harmonic oscillator with variable mass and frequency. These time-dependent displaced and squeezed number states are obtained by first squeezing and then displacing the exact number states and are exact solutions of the Schr\\"{o}dinger equation. Further, these wave functions are the time-dependent squeezed harmonic-oscillator wave functions centered at classical trajectories.

  14. In-plane displacement measurement in vortex metrology

    Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, N??stor

    2013-01-01

    Recently we proposed an alternative method of displacement analysis in vortex metrology, based on the application of the Fourier optics techniques, that is suitable for an intermediate range of displacement measurements ranging below the resolution of speckle photography and above that of the conventional vortex metrology. However, for smaller displacements, we introduce an approach to perform the Fourier analysis from vortex networks. In this work, we present an enhanced method for measuring...

  15. Ultrafast laser ablation for targeted atherosclerotic plaque removal

    Lanvin, Thomas; Conkey, Donald B.; Descloux, Laurent; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-07-01

    Coronary artery disease, the main cause of heart disease, develops as immune cells and lipids accumulate into plaques within the coronary arterial wall. As a plaque grows, the tissue layer (fibrous cap) separating it from the blood flow becomes thinner and increasingly susceptible to rupturing and causing a potentially lethal thrombosis. The stabilization and/or treatment of atherosclerotic plaque is required to prevent rupturing and remains an unsolved medical problem. Here we show for the first time targeted, subsurface ablation of atherosclerotic plaque using ultrafast laser pulses. Excised atherosclerotic mouse aortas were ablated with ultrafast near-infrared (NIR) laser pulses. The physical damage was characterized with histological sections of the ablated atherosclerotic arteries from six different mice. The ultrafast ablation system was integrated with optical coherence tomography (OCT) imaging for plaque-specific targeting and monitoring of the resulting ablation volume. We find that ultrafast ablation of plaque just below the surface is possible without causing damage to the fibrous cap, which indicates the potential use of ultrafast ablation for subsurface atherosclerotic plaque removal. We further demonstrate ex vivo subsurface ablation of a plaque volume through a catheter device with the high-energy ultrafast pulse delivered via hollow-core photonic crystal fiber.

  16. Laser ablation synthesis and spectral characterization of ruby nanoparticles

    Baranov, M. S.; Bardina, A. A.; Savelyev, A. G.; Khramov, V. N.; Khaydukov, E. V.

    2016-04-01

    The laser ablation method was implemented for synthesis of ruby nanoparticles. Nanoparticles were obtained by nanosecond ablation of bulk ruby crystal in 10% ethanol water solution. The nanoparticles enable water colloid stability and exhibit narrow photoluminescent line at 694 nm when pumped at blue-green spectral range. The ruby nanoparticles were characterized by SEM and Z-sizer.

  17. Mitral valve perforation appearing years after radiofrequency ablation

    Fisch-Thomsen, Marie; Jensen, Jesper K; Egeblad, Henrik;

    2011-01-01

    The case is reported of a young adult with Wolff-Parkinson-White (WPW) syndrome who, three years after a complicated radiofrequency (RF) catheter ablation procedure, developed dyspnea on exertion. Echocardiography revealed severe mitral valve regurgitation caused by a perforation of the posterior...... leaflet. Echocardiographic follow up is recommended after a complicated course of left-sided catheter ablation....

  18. Transonic ablation flow regimes of high-Z pellets

    Kim, Hyoungkeun; Parks, Paul

    2015-01-01

    In this letter, we report results of numerical studies of the ablation of argon and neon pellets in tokamaks and compare them with theoretical predictions and studies of deuterium pellets. Results demonstrate the influence of atomic physics processes on the pellet ablation process.

  19. Delayed Development of Pneumothorax After Pulmonary Radiofrequency Ablation

    Acute pneumothorax is a frequent complication after percutaneous pulmonary radiofrequency (RF) ablation. In this study we present three cases showing delayed development of pneumothorax after pulmonary RF ablation in 34 patients. Our purpose is to draw attention to this delayed complication and to propose a possible approach to avoid this major complication. These three cases occurred subsequent to 44 CT-guided pulmonary RF ablation procedures (6.8%) using either internally cooled or multitined expandable RF electrodes. In two patients, the pneumothorax, being initially absent at the end of the intervention, developed without symptoms. One of these patients required chest drain placement 32 h after RF ablation, and in the second patient therapy remained conservative. In the third patient, a slight pneumothorax at the end of the intervention gradually increased and led into tension pneumothorax 5 days after ablation procedure. Underlying bronchopleural fistula along the coagulated former electrode track was diagnosed in two patients. In conclusion, delayed development of pneumothorax after pulmonary RF ablation can occur and is probably due to underlying bronchopleural fistula, potentially leading to tension pneumothorax. Patients and interventionalists should be prepared for delayed onset of this complication, and extensive track ablation following pulmonary RF ablation should be avoided.

  20. Lung tumour ablation – where are we now?

    Gillams, A

    2008-01-01

    Abstract Ablation of lung tumours is the fastest expanding area within interventional oncology. Radiofrequency, laser, microwave and cryotherapy have all been shown to be effective. Which of these ablation technologies becomes the preferred technique for lung tumours remains to be seen.

  1. A New Ablative Heat Shield Sensor Suite Project

    Bose, Deepak

    2014-01-01

    A new sensor suite is developed to measure performance of ablative thermal protection systems used in planetary entry vehicles for robotic and human exploration. The new sensor suite measures ablation of the thermal protection system under extreme heating encountered during planetary entry. The sensor technology is compatible with a variety of thermal protection materials, and is applicable over a wide range of entry conditions.

  2. Studying Landslide Displacements in Megamendung (Indonesia Using GPS Survey Method

    Hasanuddin Z. Abidin

    2004-11-01

    Full Text Available Landslide is one of prominent geohazards that frequently affects Indonesia, especially in the rainy season. It destroys not only environment and property, but usually also causes deaths. Landslide monitoring is therefore very crucial and should be continuously done. One of the methods that can have a contribution in studying landslide phenomena is repeated GPS survey method. This paper presents and discusses the operational performances, constraints and results of GPS surveys conducted in a well known landslide prone area in West Java (Indonesia, namely Megamendung, the hilly region close to Bogor. Three GPS surveys involving 8 GPS points have been conducted, namely on April 2002, May 2003 and May 2004, respectively. The estimated landslide displacements in the area are relatively quite large in the level of a few dm to a few m. Displacements up to about 2-3 m were detected in the April 2002 to May 2003 period, and up to about 3-4 dm in the May 2003 to May 2004 period. In both periods, landslides in general show the northwest direction of displacements. Displacements vary both spatially and temporally. This study also suggested that in order to conclude the existence of real and significant displacements of GPS points, the GPS estimated displacements should be subjected to three types of testing namely: the congruency test on spatial displacements, testing on the agreement between the horizontal distance changes with the predicted direction of landslide displacement, and testing on the consistency of displacement directions on two consecutive periods.

  3. Locally ablative therapies for primary and metastatic liver cancer.

    Li, David; Kang, Josephine; Madoff, David C

    2014-08-01

    Locally ablative therapies have an increasing role in the effective multidisciplinary approach towards the treatment of both primary and metastatic liver tumors. In patients who are not considered surgical candidates and have low volume disease, these therapies have now become established into consensus practice guidelines. A large range of therapeutic options exist including percutaneous ethanol injection (PEI), radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, percutaneous laser ablation (PLA), irreversible electroporation (IRE), stereotactic body radiation therapy (SBRT) and high intensity focused ultrasound (HIFU); each having benefits and drawbacks. The greatest body of evidence supporting clinical utility in the liver currently exists for RFA, with PEI having fallen out of favor. MWA, IRE, SBRT and HIFU are relatively nascent technologies, and outcomes data supporting their use is promising. Future directions of ablative therapies include tandem approaches to improve efficacy in the treatment of liver tumors. PMID:24746315

  4. Chemothermal Therapy for Localized Heating and Ablation of Tumor

    Zhong-Shan Deng

    2013-01-01

    Full Text Available Chemothermal therapy is a new hyperthermia treatment on tumor using heat released from exothermic chemical reaction between the injected reactants and the diseased tissues. With the highly minimally invasive feature and localized heating performance, this method is expected to overcome the ubiquitous shortcomings encountered by many existing hyperthermia approaches in ablating irregular tumor. This review provides a relatively comprehensive review on the latest advancements and state of the art in chemothermal therapy. The basic principles and features of two typical chemothermal ablation strategies (acid-base neutralization-reaction-enabled thermal ablation and alkali-metal-enabled thermal/chemical ablation are illustrated. The prospects and possible challenges facing chemothermal ablation are analyzed. The chemothermal therapy is expected to open many clinical possibilities for precise tumor treatment in a minimally invasive way.

  5. Pulsed laser ablation of solids basics, theory and applications

    Stafe, Mihai; Puscas, Niculae N

    2014-01-01

    The book introduces ‘the state of the art' of pulsed laser ablation and its applications. It is based on recent theoretical and experimental studies. The book reaches from the basics to advanced topics of pulsed laser ablation. Theoretical and experimental fundamental phenomena involved in pulsed laser ablation are discussed with respect to material properties, laser wavelength, fluence and intensity regime of the light absorbed linearly or non-linearly in the target material. The energy absorbed by the electrons leads to atom/molecule excitation, ionization and/or direct chemical bond breaking and is also transferred to the lattice leading to material heating and phase transitions. Experimental  non-invasive optical methods for analyzing these phenomena in real time are described. Theoretical models for pulsed laser ablation and phase transitions induced by laser beams and laser-vapour/plasma interaction during the plume expansion above the target are also presented. Calculations of the ablation speed and...

  6. Synthesis of nanocrystalline cubic zirconia using femtosecond laser ablation

    We report on the synthesis of nanocrystalline zirconia in liquid using femtosecond laser ablation. Nanocrystalline cubic zirconia has been prepared by femtosecond laser ablation of zirconium in ammonia, while nanocrystalline tetragonal and monoclinic zirconia was synthesized in water. The physical and chemical mechanisms of the formation of nanocrystalline metastable zirconia are discussed. The intrinsic properties of femtosecond laser ablation in liquid and OH−1 may be responsible for the synthesis of cubic zirconia. It is suggested that the femtosecond laser pulse can create higher temperature and pressure conditions at a localized area in the liquid than the nanosecond laser pulse and the cooling is also faster in the femtosecond laser ablation process, which determined the difference between the products synthesized with femtosecond and nanosecond-pulsed laser ablation.

  7. Ablation of CsI by XUV Capillary Discharge Laser

    Pira, Peter; Zelinger, Zdenek; Burian, Tomas; Vysin, Ludek; Wild, Jan; Juha, Libor; Lancok, Jan; Nevrly, Vaclav

    2015-09-01

    XUV capillary discharge laser (CDL) is suitable source for ablation of ionic crystals as material which is difficult to ablate by conventional laser. Single crystal of CsI was irradiated by 2.5 ns pulses of a 46.9 nm radiation at 2 Hz. The CDL beam was focused by Sc/Si multilayer spherical mirror. Attenuation length of CsI for this wavelength is 38 nm. Ablation rate was calculated after irradiation of 10, 20, 30, 50 and 100 pulses. Depth of the craters was measured by optical profiler (white light interferometry). Ablation threshold was determined from craters after irradiation with the changing fluence and compared with modeling by XUV-ABLATOR.

  8. Imaging evaluation of liver cancer after radiofrequency ablation therapy

    Radiofrequency ablation has been an important means of the comprehensive therapy for liver cancers, especially for the treatment of small hepatocellular carcinomas. Radiofrequency ablation has already showed encouraging clinical effects. However, due to the limitation of ablation extent the remnants of tumor lesions or the recurrence of tumor are often seen. Therefore, it is very important to accurately evaluate the curative effect of radiofrequency ablation. This paper aims to summarize the evaluation of curative effect of radiofrequency ablation with different imaging methods, and to discuss the advantages and disadvantages of these different imaging methods in order to provide a correct reference for taking reasonable imaging means to help make the proper clinical treatment. (authors)

  9. Synthesis of Ag@Silica Nanoparticles by Assisted Laser Ablation.

    González-Castillo, J R; Rodriguez, E; Jimenez-Villar, E; Rodríguez, D; Salomon-García, I; de Sá, Gilberto F; García-Fernández, T; Almeida, D B; Cesar, C L; Johnes, R; Ibarra, Juana C

    2015-12-01

    This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag(+) concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM). PMID:26464175

  10. Nanoparticle fabrication of hydroxyapatite by laser ablation in water

    Synthetic polycrystalline hydroxyapatite was ablated in water with 337 nm radiation from a UV nitrogen pulsed laser. According to transmission electron microscopy micrographs, the ablated particles were approximately spherical and had a size of ∼80 nm. Raman spectroscopic analysis demonstrated that particles had the same structure as the original crystal. X-ray photoelectron spectroscopy showed that the surface chemical composition was close to that of the original material. The characteristics of the ablated particles and estimations of the temperature rise of the hydroxyapatite surface under laser irradiation are consistent with the mechanism of explosive boiling being responsible for ablation. The experimental observations offer the basis for preparation of hydroxyapatite nanoparticles by laser ablation in water

  11. Disruptions and vertical displacement events in JET

    Major disruptions and vertical displacement events (VDEs) represent a serious problem for the integrity of large devices such as ITER and a reactor. This arises from the localized power deposition on the divertor target and first wall, the production of runaway electrons in the post-disruptive plasma and the substantial forces transmitted to the vacuum vessel by eddy and halo currents. Extensive experiments have been performed in JET to characterize the phenomena associated with disruptions and VDEs and to investigate the underlying physics. In addition, the installation of a disruption feedback stabilization system based on a set of four internal saddle coils driven by high power (3 kA/1.5 kV), high frequency (0-10 kHz) amplifiers has allowed initial experiments on the control of disruptions by suppression of the n = 1 mhd precursor. This system has also been used to study fundamental aspects of the physics of error field induced modes, which is of direct application to ITER (author). 3 refs, 8 figs

  12. The Three Gorges: the unexamined toll of development-induced displacement

    Martin Stein

    1998-04-01

    Full Text Available In China, the context of forced displacement in its broadest sense centres on four issues: (1 coercive displacement for development; (2 political persecution resulting in controlled displacement; (3 massive labour dislocations; and (4 disaster-induced displacement. This article looks at the role of the state in displacement, focusing on the first of these issues: development-induced displacement.

  13. HIFU Tissue Ablation: Concept and Devices.

    Ter Haar, Gail

    2016-01-01

    High intensity focused ultrasound (HIFU) is rapidly gaining clinical acceptance as a technique capable of providing non-invasive heating and ablation for a wide range of applications. Usually requiring only a single session, treatments are often conducted as day case procedures, with the patient either fully conscious, lightly sedated or under light general anesthesia. HIFU scores over other thermal ablation techniques because of the lack of necessity for the transcutaneous insertion of probes into the target tissue. Sources placed either outside the body (for treatment of tumors or abnormalities of the liver, kidney, breast, uterus, pancreas brain and bone), or in the rectum (for treatment of the prostate), provide rapid heating of a target tissue volume, the highly focused nature of the field leaving tissue in the ultrasound propagation path relatively unaffected. Numerous extra-corporeal, transrectal and interstitial devices have been designed to optimize application-specific treatment delivery for the wide-ranging areas of application that are now being explored with HIFU. Their principle of operation is described here, and an overview of their design principles is given. PMID:26486329

  14. Laser Ablation of Polymer Microfluidic Devices

    Killeen, Kevin

    2004-03-01

    Microfluidic technology is ideal for processing precious samples of limited volumes. Some of the most important classes of biological samples are both high in sample complexity and low in concentration. Combining the elements of sample pre-concentration, chemical separation and high sensitivity detection with chemical identification is essential for realizing a functional microfluidic based analysis system. Direct write UV laser ablation has been used to rapidly fabricate microfluidic devices capable of high performance liquid chromatography (HPLC)-MS. These chip-LC/MS devices use bio-compatible, solvent resistant and flexible polymer materials such as polyimide. A novel microfluidic to rotary valve interface enables, leak free, high pressure fluid switching between multiple ports of the microfluidic chip-LC/MS device. Electrospray tips with outer dimension of 50 um and inner of 15 um are formed by ablating the polymer material concentrically around a multilayer laminated channel structure. Biological samples of digested proteins were used to evaluate the performance of these microfluidic devices. Liquid chromatography separation and similar sample pretreatments have been performed using polymeric microfluidic devices with on-chip separation channels. Mass spectrometry was performed using an Agilent Technologies 1100 series ion trap mass spectrometer. Low fmol amounts of protein samples were positively and routinely identified by searching the MS/MS spectral data against protein databases. The sensitivity and separation performance of the chip-LC devices has been found to be comparable to state of the art nano-electrospray systems.

  15. Radiofrequency Ablation of Intrahepatic Cholangiocarcinoma: Preliminary Experience

    The purpose of this study was to evaluate the safety and efficacy of percutaneous ultrasound (US)-guided radiofrequency ablation (RFA) in patients with intrahepatic cholangiocarcinoma (ICCA) in a small, nonrandomized series. From February 2004 to July 2008, six patients (four men and two women; mean age 69.8 years [range 48 to 83]) with ICCA underwent percutaneous US-guided RFA. Preintervetional transarterial embolization was performed in two cases to decrease heat dispersion during RFA in order to increase the area of ablation. The efficacy of RFA was evaluated using contrast-enhanced dynamic computed tomography (CT) 1 month after treatment and then every 3 months thereafter. Nine RFA sessions were performed for six solid hepatic tumors in six patients. The duration of follow-up ranged from 13 to 21 months (mean 17.5). Posttreatment CT showed total necrosis in four of six tumors after one or two RFA sessions. Residual tumor was observed in two patients with larger tumors (5 and 5.8 cm in diameter). All patients tolerated the procedure, and there with no major complications. Only 1 patient developed post-RFA syndrome (pain, fever, malaise, and leukocytosis), which resolved with oral administration of acetaminophen. Percutaneous RFA is a safe and effective treatment for patients with hepatic tumors: It is ideally suited for those who are not eligible for surgery. Long-term follow-up data regarding local and systemic recurrence and survival are still needed.

  16. Radiofrequency ablation of intrahepatic cholangiocarcinoma: preliminary experience.

    Carrafiello, Gianpaolo; Laganà, Domenico; Cotta, Elisa; Mangini, Monica; Fontana, Federico; Bandiera, Francesca; Fugazzola, Carlo

    2010-08-01

    The purpose of this study was to evaluate the safety and efficacy of percutaneous ultrasound (US)-guided radiofrequency ablation (RFA) in patients with intrahepatic cholangiocarcinoma (ICCA) in a small, nonrandomized series. From February 2004 to July 2008, six patients (four men and two women; mean age 69.8 years [range 48 to 83]) with ICCA underwent percutaneous US-guided RFA. Preintervetional transarterial embolization was performed in two cases to decrease heat dispersion during RFA in order to increase the area of ablation. The efficacy of RFA was evaluated using contrast-enhanced dynamic computed tomography (CT) 1 month after treatment and then every 3 months thereafter. Nine RFA sessions were performed for six solid hepatic tumors in six patients. The duration of follow-up ranged from 13 to 21 months (mean 17.5). Posttreatment CT showed total necrosis in four of six tumors after one or two RFA sessions. Residual tumor was observed in two patients with larger tumors (5 and 5.8 cm in diameter). All patients tolerated the procedure, and there with no major complications. Only 1 patient developed post-RFA syndrome (pain, fever, malaise, and leukocytosis), which resolved with oral administration of acetaminophen. Percutaneous RFA is a safe and effective treatment for patients with hepatic tumors: It is ideally suited for those who are not eligible for surgery. Long-term follow-up data regarding local and systemic recurrence and survival are still needed. PMID:20411389

  17. Producing Uniform Lesion Pattern in HIFU Ablation

    Zhou, Yufeng; Kargl, Steven G.; Hwang, Joo Ha

    2009-04-01

    High intensity focused ultrasound (HIFU) is emerging as a modality for treatment of solid tumors. The temperature at the focus can reach over 65° C denaturing cellular proteins resulting in coagulative necrosis. Typically, HIFU parameters are the same for each treated spot in most HIFU control systems. Because of thermal diffusion from nearby spots, the size of lesions will gradually become larger as the HIFU therapy progresses, which may cause insufficient treatment of initial spots, and over-treatment of later ones. It is found that the produced lesion pattern also depends on the scanning pathway. From the viewpoint of the physician creating uniform lesions and minimizing energy exposure are preferred in tumor ablation. An algorithm has been developed to adaptively determine the treatment parameters for every spot in a theoretical model in order to maintain similar lesion size throughout the HIFU therapy. In addition, the exposure energy needed using the traditional raster scanning is compared with those of two other scanning pathways, spiral scanning from the center to the outside and from the outside to the center. The theoretical prediction and proposed algorithm were further evaluated using transparent gel phantoms as a target. Digital images of the lesions were obtained, quantified, and then compared with each other. Altogether, dynamically changing treatment parameters can improve the efficacy and safety of HIFU ablation.

  18. CT Guided Laser Ablation of Osteoid Osteoma

    Manohar Kachare

    2015-10-01

    Full Text Available To present our experience of Computed Tomography (CT guided laser ablation of radiologically proven osteoid osteoma in the inter trochantric region of the femur. A19 year old female presented with severe pain in left upper thigh region since 6-7 months, which was exaggerated during nights and was relived on taking oral Non Steroid Anti Inflammatory Drugs (NSAIDs. On CT scan hypodense lesion with surrounding dense sclerosis noted in intertrochanteric region in left femur. Magnetic Resonance Imaging (MRI revealed small focal predominantly cortical, oval lytic lesion in the intertrochanteric region which appeared hypointense on T1 Weighted Image (T1WI and hyperintense on T2 Weighted Image (T2WI and Short Tau Inversion Recovery (STIR image. Diffuse extensive sclerosis and hyperostosis of bone was noted surrounding the lesion appearing hypointense on T1W and T2W images. Under local anesthesia the laser fibre was inserted in the nidus under CT guidance through bone biopsy needle and 1800 joules energy delivered in the lesion continuous mode. Complete relief of pain noted after 24 hours after the treatment. CT guided LASER ablation is a safe, simple and effective method of treatment for osteoid osteoma.

  19. Printable Nanophotonic Devices via Holographic Laser Ablation.

    Zhao, Qiancheng; Yetisen, Ali K; Sabouri, Aydin; Yun, Seok Hyun; Butt, Haider

    2015-09-22

    Holography plays a significant role in applications such as data storage, light trapping, security, and biosensors. However, conventional fabrication methods remain time-consuming, costly, and complex, limiting the fabrication of holograms and their extensive use. Here, we demonstrate a single-pulse laser ablation technique to write parallel surface gratings and Fresnel zone plates. We utilized a 6 ns high-energy green laser pulse to form interference patterns to record a surface grating with 820 nm periodicity and asymmetric zone plate holograms on 4.5 nm gold-coated substrates. The holographic recording process was completed within seconds. The optical characteristics of the interference patterns have been computationally modeled, and well-ordered polychromatic diffraction was observed from the fabricated holograms. The zone plate showed a significant diffraction angle of 32° from the normal incident for the focal point. The nanosecond laser interference ablation for rapid hologram fabrication holds great potential in a vast range of optical devices. PMID:26301907

  20. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    Every, A. G.; Utegulov, Z. N.; Veres, I. A.

    2015-03-01

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  1. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    Every, A. G., E-mail: arthur.every@wits.ac.za [School of Physics, University of the Witwatersrand, PO Wits 2050 (South Africa); Utegulov, Z. N., E-mail: zhutegulov@nu.edu.kz [Department of Physics, School of Science and Technology, Nazarbayev University, Astana 010000 (Kazakhstan); Veres, I. A., E-mail: istvan.veres@recendt.at [RECENDT Research Center for Non Destructive Testing GmbH, A-4040 Linz (Austria)

    2015-03-31

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

  2. Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

    The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point

  3. Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields

    Xie, Fei; Varghese, Frency; Pakhomov, Andrei G.; Semenov, Iurii; Xiao, Shu; Philpott, Jonathan; Zemlin, Christian

    2015-01-01

    Background Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations. Methods We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2–4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5–20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12–18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume. Results In all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters. Conclusions Ablation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation. PMID:26658139

  4. Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields.

    Fei Xie

    Full Text Available Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs can potentially overcome these limitations.We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12. We repeatedly inserted two shock electrodes, spaced 2-4 mm apart, into the ventricles (through the entire wall and applied nanosecond pulsed electric fields (nsPEF (5-20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies to create linear lesions of 12-18 mm length. Hearts were stained either with tetrazolium chloride (TTC or propidium iodide (PI to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume.In all animals (12/12, we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters.Ablation with nsPEFs is a promising alternative to radiofrequency (RF ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation.

  5. Percutaneous Renal Tumor Ablation: Radiation Exposure During Cryoablation and Radiofrequency Ablation

    IntroductionOnce reserved solely for non-surgical cases, percutaneous ablation is becoming an increasingly popular treatment option for a wider array of patients with small renal masses and the radiation risk needs to be better defined as this transition continues.Materials and MethodsRetrospective review of our renal tumor ablation database revealed 425 patients who underwent percutaneous ablation for treatment of 455 renal tumors over a 5-year time period. Imparted radiation dose information was reviewed for each procedure and converted to effective patient dose and skin dose using established techniques. Statistical analysis was performed with each ablative technique.ResultsFor the 331 cryoablation procedures, the mean DLP was 6987 mGycm (SD = 2861) resulting in a mean effective dose of 104.7 mSv (SD = 43.5) and the mean CTDIvol was 558 mGy (SD = 439) resulting in a mean skin dose of 563.2 mGy (SD = 344.1). For the 124 RFA procedures, the mean DLP was 3485 mGycm (SD = 1630) resulting in a mean effective dose of 50.3 mSv (SD = 24.0) and the mean CTDIvol was 232 mGy (SD = 149) resulting in a mean skin dose of 233.2 mGy (SD = 117.4). The difference in patient radiation exposure between the two renal ablation techniques was statistically significant (p < 0.001).ConclusionBoth cryoablation and RFA imparted an average skin dose that was well below the 2 Gy deterministic threshold for appreciable sequela. Renal tumor cryoablation resulted in a mean skin and effective radiation dose more than twice that for RFA. The radiation exposure for both renal tumor ablation techniques was at the high end of the medical imaging radiation dose spectrum

  6. Percutaneous Renal Tumor Ablation: Radiation Exposure During Cryoablation and Radiofrequency Ablation

    McEachen, James C., E-mail: james.mceachen2@gmail.com [Mayo Clinic, Division of Preventive, Occupational, and Aerospace Medicine (United States); Leng, Shuai; Atwell, Thomas D. [Mayo Clinic, Department of Radiology (United States); Tollefson, Matthew K. [Mayo Clinic, Department of Urology (United States); Friese, Jeremy L. [Mayo Clinic, Department of Radiology (United States); Wang, Zhen; Murad, M. Hassan [Mayo Clinic, Division of Preventive, Occupational, and Aerospace Medicine (United States); Schmit, Grant D. [Mayo Clinic, Department of Radiology (United States)

    2016-02-15

    IntroductionOnce reserved solely for non-surgical cases, percutaneous ablation is becoming an increasingly popular treatment option for a wider array of patients with small renal masses and the radiation risk needs to be better defined as this transition continues.Materials and MethodsRetrospective review of our renal tumor ablation database revealed 425 patients who underwent percutaneous ablation for treatment of 455 renal tumors over a 5-year time period. Imparted radiation dose information was reviewed for each procedure and converted to effective patient dose and skin dose using established techniques. Statistical analysis was performed with each ablative technique.ResultsFor the 331 cryoablation procedures, the mean DLP was 6987 mGycm (SD = 2861) resulting in a mean effective dose of 104.7 mSv (SD = 43.5) and the mean CTDI{sub vol} was 558 mGy (SD = 439) resulting in a mean skin dose of 563.2 mGy (SD = 344.1). For the 124 RFA procedures, the mean DLP was 3485 mGycm (SD = 1630) resulting in a mean effective dose of 50.3 mSv (SD = 24.0) and the mean CTDI{sub vol} was 232 mGy (SD = 149) resulting in a mean skin dose of 233.2 mGy (SD = 117.4). The difference in patient radiation exposure between the two renal ablation techniques was statistically significant (p < 0.001).ConclusionBoth cryoablation and RFA imparted an average skin dose that was well below the 2 Gy deterministic threshold for appreciable sequela. Renal tumor cryoablation resulted in a mean skin and effective radiation dose more than twice that for RFA. The radiation exposure for both renal tumor ablation techniques was at the high end of the medical imaging radiation dose spectrum.

  7. A Reference Optical System of Laser Doppler Longitudinal Displacement Measurement

    张存满; 赵洋; 李达成

    2001-01-01

    In this paper, a new reference optical system is put forward to achieve longitudinal displacement measurement. An optical grating is used for frequency mixing and getting high SNR signals in the measurement. Conditions and methods for getting Doppler beat signals are presented.The experiments indicate that this optical syetem can be used to measure the longitudinal displacement with high accuracy.

  8. Employment protection and the consequences for displaced workers

    Albæk, Karsten; van Audenrode, Marc; Browning, Martin

    We compare the wage and employment consequences of a job displacement in Belgium and Denmark. These two countries both have generous unemployment insurance schemes but job protection laws vary dramatically between the two. Using comparable data we find that the incidence of displacement and the...

  9. Isothermal Gas assisted displacement of a polystyrene melt

    Eriksson, Torbjörn Gerhard; Rasmussen, Henrik K.

    2007-01-01

    Isothermal gas displacements of a polystyrene melt (shaped as circular cylinder with a radius of 2.5mm) placed inside a circular steel annulus were performed. A flow valve ensures a constant flow rate and rotational symmetric flow during the displacement. The experiments show an increase in the...

  10. Gas dynamic characteristic of displacer in Stirling cryocoolers

    Xinguang LIU; Dongyu LIU; Yong WANG; Yinong WU

    2008-01-01

    Based on the vector analysis of the dynamic characteristic of the displacer in split-type Stirling cryo-coolers, experimental study was performed on a 2 W@80 K cooler to uncover the relationship among pressure fluctuation, damped impedance, inherent fre-quency, cold-tip temperature and the cooling perform-ance. The result shows that the pressure amplitude and phase shift between pressure and displacer motion decrease when the cooling temperature decreases; the dynamic damp of the displacer increases at lower cooling temperature, which results in the increase of pressure drop of the regenerator, the decrease of average pressure of the cold cubage, the decrease of gas dynamic pressure, the decrease of phase shift between pressure and displacer motion, and the displacement of the regenerator and the PV power; at lower cooling temperature, the inherent fre-quency of the displacer increases because of the augmen-tation of gas spring constant. And as the inherent frequency is getting closer to the operating frequency, the drive current of the motor decreases; the piston of the compressor affects the displacer by the pressure fluc-tuation engendered by its motion, and the displacer reacts by changing the mass and momentum distribution to adjust the gas spring constant and the damp coefficient.

  11. A displacement based FE formulation for steady state problems

    Yu, Yuhong

    2005-01-01

    In this thesis a new displacement based formulation is developed for elasto-plastic deformations in steady state problems. In this formulation the displacements are the primary variables, which is in contrast to the more common formulations in terms of the velocities as the primary variables. In a s

  12. Study on the applicability of the desk displacement ventilation concept

    Loomans, Marcel G.L.C.

    1999-01-01

    This paper summarizes an experimental and numerical study into a ventilation concept that combines displacement ventilation with task conditioning, the so-called desk displacement ventilation (DDV) concept. The study uses steady-state and transient results to discuss the applicability of the DDV con

  13. Displacement Ventilation in a Room with Low-Level Diffusers

    Nielsen, Peter V.

    Ventilation systems with vertical displacement flow have been used in industrial areas with high thermal loads for many years. Quite resently the vertical displacement flow systems have grown popular as comfort ventilation in rooms with thermal loads e.g. offices....

  14. Displacement and Force Measurements with Quadrant Photodetector in Optical Tweezers

    郭红莲; 刘春香; 李兆霖; 段建发; 韩学海; 程丙英; 张道中

    2003-01-01

    A technique of displacement and force measurements with a photodiode quadrant detector in an optical tweezers system is presented. The stiffness of optical trap is calibrated and the leukemia cell membrane tension is measured.The results show that the optical tweezers combined with the quadrant detector is a very useful tool for detecting the displacement and force with a millisecond-order response.

  15. Hyoid Displacement in Post-Treatment Cancer Patients: Preliminary Findings

    Zu, Yihe; Yang, Zhenyu; Perlman, Adrienne L.

    2011-01-01

    Purpose: Dysphagia after head and neck cancer treatment is a health care issue; in some cases, the cause of death is not cancer but, rather, the passage of food or liquid into the lungs. Hyoid displacement is known to be important to safe swallowing function. The purpose of this study was to evaluate hyoid displacement after cancer treatment.…

  16. Predicting target displacements using ultrasound elastography and finite element modeling

    Buijs, J.O. den; Hansen, H.H.G.; Lopata, R.G.P.; Korte, C.L. de; Misra, S.

    2011-01-01

    Soft tissue displacements during minimally invasive surgical procedures may cause target motion and subsequent misplacement of the surgical tool. A technique is presented to predict target displacements using a combination of ultrasound elastography and finite element (FE) modeling. A cubic gelatin/

  17. 48 CFR 952.226-74 - Displaced employee hiring preference.

    2010-10-01

    ... Displaced employee hiring preference. As prescribed in 48 CFR (DEAR) 926.7104, insert the following clause. Displaced Employee Hiring Preference (JUN 1997) (a) Definition. Eligible employee means a current or former... preference. 952.226-74 Section 952.226-74 Federal Acquisition Regulations System DEPARTMENT OF ENERGY...

  18. Simultaneous sensing of displacement and temperature with a single FBG

    WEI Ting; QIAO Xue-guang; JIA Zhen-an

    2011-01-01

    @@ A novel fiber Bragg grating (FBG) sensor with simultaneous sensing of displacement and temperature is presented.The FBG is affixed on the cantilever inclinedly.The midpoint of FBG exactly coincides with the zero strain layer of a rectangular beam.The vertical displacement can be measured by the broadened bandwidth of FBG as the bandwidth is insensitive to temperature, while the temperature can be measured by the center wavelength shift as the wavelength shift is insensitive to vertical displacement.With 0.1 nm spectral resolution of the analyzer, sensitivities of bandwidth-displacement and center wavelength-temperature are 0.48 nm/mm and 0.05 nm/℃, resolutions are 0.2 mm and 2.0 ℃, and sensing ranges of displacement and temperature are up to 8.5 mm and 45℃ respectively.Experimental results match theoretical analyses very well.

  19. POST TRAUMATIC DISPLACEMENT OF TESTIS- A RARE CASE REPORT

    Avadhut

    2013-03-01

    Full Text Available ABSTRACT: Traumatic displacement of the testis is a rare occur rence and is defined as the displacement of one or both testis to a position othe r than the scrotum (1 .Traumatic displacement of testis is commonly a delayed diagnos is during treatment occurs as a consequence of high velocity road traffic accident (2 usually following a motorcycle collision, in what is referred to as "fuel tank injury”. Early id entification and subsequent surgical management is of utmost importance to maintain norm al spermatogenesis in the displaced testis. We report a case of traumatic displacement o f testis in superficial inguinal pouch in a young man presented 1 year after a road traffic acci dent. The clinical diagnosis was well supported by USG. The patient was successfully treated by inguinal exploration and repositioning of testis in scrotum, under spinal anes thesia.

  20. Synthetic-wavelength self-mixing interferometry for displacement measurement

    Chen, Junbao; Zhu, Hongbin; Xia, Wei; Guo, Dongmei; Hao, Hui; Wang, Ming

    2016-06-01

    A simple synthetic-wavelength self-mixing interferometer is proposed for precision displacement measurement. Choosing the frequency difference of the orthogonally polarized dual frequency He-Ne laser appropriately, we introduce synthetic wavelength theory into self-mixing interference principle and demonstrate a feasible optical configuration by simply adjusting the optical design of self-mixing interferometer. The phase difference between the two orthogonally polarized feedback fringes is observed, and the tiny displacement of the object can be measured through the phase change of the synthetic signal. Since the virtual synthetic wavelength is 106 times larger than the operating wavelength, sub-nanometer displacement of the object can be obtained in millimeter criterion measurement without modulation, demodulation and complicated electrical circuits. Experimental results verifies the synthetic wavelength self-mixing interferometer's ability of measuring nanoscale displacement, which provides a potential approach for contactless precision displacement measurement in a number of scientific and industrial applications.

  1. Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator

    Milos, F. S.; Chen, Y.-K.

    2009-01-01

    Phenolic Impregnated Carbon Ablator was the heatshield material for the Stardust probe and is also a candidate heatshield material for the Orion Crew Module. As part of the heatshield qualification for Orion, physical and thermal properties were measured for newly manufactured material, included emissivity, heat capacity, thermal conductivity, elemental composition, and thermal decomposition rates. Based on these properties, an ablation and thermal-response model was developed for temperatures up to 3500 K and pressures up to 100 kPa. The model includes orthotropic and pressure-dependent thermal conductivity. In this work, model validation is accomplished by comparison of predictions with data from many arcjet tests conducted over a range of stagnation heat flux and pressure from 107 Watts per square centimeter at 2.3 kPa to 1100 Watts per square centimeter at 84 kPa. Over the entire range of test conditions, model predictions compare well with measured recession, maximum surface temperatures, and in depth temperatures.

  2. Neutral and plasma shielding model for pellet ablation

    The neutral gas shielding model for ablation of frozen hydrogenic pellets is extended to include the effects of an initial Maxwelliam distribution of incident electron energies; a cold plasma shield outside the neutral shield and extended along the magnetic field; energetic neutral beam ions and alpha particles; and self-limiting electron ablation in the collisionless plasma limit. Including the full electron distribution increases ablation, but adding the cold ionized shield reduces ablation; the net effect is a modest reduction in pellet penetration compared with the monoenergetic electron neutral shielding model with no plasma shield. Unlike electrons, fast ions can enter the neutral shield directly without passing through the cold ionized shield because their gyro-orbits are typically larger than the diameter of the cold plasma tube. Fast alpha particles should not enhance the ablation rate unless their population exceeds that expected from local classical thermalization. Fast beam ions, however, may enhance ablation in the plasma periphery if their population is high enough. Self-limiting ablation in the collisionless limit leads to a temporary distortion of the original plasma electron Maxwellian distribution function through preferential depopulation of the higher-energy electrons. 23 refs., 9 figs

  3. Actual role of radiofrequency ablation of liver metastases

    Pereira, Philippe L. [Eberhard-Karls-University of Tuebingen, Department of Diagnostic Radiology, Tuebingen (Germany)

    2007-08-15

    The liver is, second only to lymph nodes, the most common site for metastatic disease irrespective of the primary tumour. More than 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improved survival in patients with colorectal metastases, only approximately 20% of patients are eligible for surgery. Thermal ablation and especially radiofrequency ablation emerge as an important additional therapy modality for the treatment of liver metastases. RF ablation shows a benefit in life expectancy and may lead in a selected patient group to cure. Percutaneous RF ablation appears safer (versus cryotherapy), easier (versus laser), and more effective (versus ethanol instillation and transarterial chemoembolisation) compared with other minimally invasive procedures. RF ablation can be performed by a percutaneous, laparoscopical or laparotomic approach, and may be potentially combined with chemotherapy and surgery. At present ideal candidates have tumours with a maximum diameter less than 3.5 cm. An untreatable primary tumour or a systemic disease represents contraindications for performing local therapies. Permanent technical improvements of thermal ablation devices and a better integration of thermal ablation in the overall patient care may lead to prognosis improvement in patients with liver metastases. (orig.)

  4. Actual role of radiofrequency ablation of liver metastases

    The liver is, second only to lymph nodes, the most common site for metastatic disease irrespective of the primary tumour. More than 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improved survival in patients with colorectal metastases, only approximately 20% of patients are eligible for surgery. Thermal ablation and especially radiofrequency ablation emerge as an important additional therapy modality for the treatment of liver metastases. RF ablation shows a benefit in life expectancy and may lead in a selected patient group to cure. Percutaneous RF ablation appears safer (versus cryotherapy), easier (versus laser), and more effective (versus ethanol instillation and transarterial chemoembolisation) compared with other minimally invasive procedures. RF ablation can be performed by a percutaneous, laparoscopical or laparotomic approach, and may be potentially combined with chemotherapy and surgery. At present ideal candidates have tumours with a maximum diameter less than 3.5 cm. An untreatable primary tumour or a systemic disease represents contraindications for performing local therapies. Permanent technical improvements of thermal ablation devices and a better integration of thermal ablation in the overall patient care may lead to prognosis improvement in patients with liver metastases. (orig.)

  5. Ablation characteristics of quantum square pulse mode dental erbium laser

    Lukač, Nejc; Suhovršnik, Tomaž; Lukač, Matjaž; Jezeršek, Matija

    2016-01-01

    Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

  6. Laser ablation of tumors: current concepts and recent developments

    Purpose. The purpose of this paper is to present technical innovations and clinical results of percutaneous interventional laser ablation of tumors using new techniques. Methods. Laser ablation was performed in 182 patients (liver tumors: 131, non hepatic tumors - bone, lung, others: 51) after interdisciplinary consensus was obtained. The procedure was done using a combination of imaging modalities (CT/MRI, CT/US) or only closed high field MRI (1.5 T). All patients received an MRI-scan immediately after laser ablation. Results. In 90.9% of the patients with liver tumors, a complete ablation was achieved. Major events occurred in 5.4%. The technical success rate of laser ablation in non-hepatic tumors was high, clinical results differed depending on the treated organ. Conclusions. The treatment of tumors of the liver and other organs up to 5 cm by laser ablation was a safe procedure with a low rate of complications and side effects. Image guidance by MRI is advantageous for precise tumor visualization in all dimensions, therapy monitoring, and control of laser ablation results. (orig.)

  7. Cryoablation versus radiofrequency ablation in AVNRT: same goal, different strategy

    Riahi Leila; Prisecaru Raluca; De Greef Yves; Stockman Dirk; Schwagten Bruno

    2015-06-01

    Full Text Available Atrioventricular nodal re-entry tachycardia (AVNRT is the most common benign supraventricular tachycardia{Kastor, 1975 #14}. The underlying substrate for the arrhythmia was first proven by Denes et al. in 1973 as being the presence of dual atrioventricular (AV pathways {Denes, 1973 #3}. Although present in about 20 to 30% of people, AV nodal duality only gives rise to symptomatic tachycardia in about 3% of this subgroup {McCanta, #18}. Therapeutic options for symptomatic patients consist of both medical therapy and ablation. Several class I, II and IV anti-arrhythmic drugs are used to treat AVNRT. However, since the majority of patients suffering from AVNRT are in their second and third decade of life, a long-lasting drug therapy is not the most preferred option. Therefore radiofrequency (RF ablation for AVNRT was introduced in 1982 by Gallagher et al {Gallagher, 1982 #7}. The initial target for ablation was the fast pathway {Langberg, 1989 #16}. This approach soon proved to have some deleterious side effects such as complete atrioventricular block in 10%-20% {Epstein, 1989 #6} and so the target for ablation was moved to the slow pathway in most patients. Nowadays two options are available to ablate the slow pathway: focal cryoablation or RF ablation. Both techniques come with different advantages and disadvantages. This paper is dedicated to make a historical comparison between both techniques, evaluate results published in literature and comment on possible pitfalls in using cryo- and RF ablation.

  8. Role of Intracardiac echocardiography in Atrial Fibrillation Ablation

    Antonio Dello Russo, MD PhD

    2013-04-01

    Full Text Available In the recent years, several new evidences support catheter-based ablation as a treatment modality of atrial fibrillation (AF. Based on a plenty of different applications, intracardiac echocardiography (ICE is now a well-established technology in complex electrophysiological procedures, in particular in AF ablation. ICE contributes to improve the efficacy and safety of such procedures defining the anatomical structures involved in ablation procedures and monitoring in real time possible complications. In particular ICE allows: a correct identification of the endocardial structures; a guidance of transseptal puncture; an assessment of accurate placement of the circular mapping catheter; an indirect evaluation of evolving lesions during radiofrequency (RF energy delivery via visualization of micro and macrobubbles tissue heating; assessment of catheter contact with cardiac tissues. Recently, also the feasibility of the integration of electroanatomical mapping (EAM and intracardiac echocardiography has been demonstrated, combining accurate real time anatomical information with electroanatomical data. As a matter of fact, different techniques and ablation strategies have been developed throughout the years. In the setting of balloon-based ablation systems, recently adopted by an increasing number of centers, ICE might have a role in the choice of appropriate balloon size and to confirm accurate occlusion of pulmonary veins. Furthermore, in the era of minimally fluoroscopic ablation, ICE has successfully provided a contribute in reducing fluoroscopy time. The purpose of this review is to summarize the current applications of ICE in catheter based ablation strategies of atrial fibrillation, focusing-on electronically phased-array ICE.

  9. Role of Percutaneous Microwave Ablation in Treatment of Hepatocellular Carcinoma

    Ahmed Tharwat Sayed *, Sahar M El Fiky*,

    2014-07-01

    Full Text Available Introduction: Hepatocellular carcinoma (HCC is one of the most common malignancies worldwide with an annual occurrence of one million new cases. An etiologic association between HBV infection and the development of HCC has been established. Hepatitis C virus is also proving an important predisposing factor for this malignancy, the use of minimally invasive Percutaneous ablative technique (e.g. Radiofrequency (RF and Microwave ablation (MW has gained great momentum and because of the drawbacks of RF ablation, several groups have successfully proved the efficacious nature of Microwave ablation in the treatment of hepatocellular carcinoma. Aim of the Work: The aim of this work is to highlight the role, the principles and the applications of percutaneous Microwave Ablation in Hepatocellular carcinoma. Methods: The studied group included 30 patients (25 men and 5 women with hepatocellular carcinoma. All patients underwent microwave ablation for the hepatocellular carcinoma. Results: The results of the procedures will be assessed as regarding sizeand enhancement of the lesion (s on triphasic CT abdomen before the procedure and at the follow up at one month as well as the Alpha fetoprotein levels. Conclusion: MWA technique represents a safe, fast and efficacious way to perform hepatic ablation in patients with HCC. Initial results are encouraging; however, longer follow-up is needed for further classification of our results.

  10. Percutaneous microwave ablation vs radiofrequency ablation in the treatment of hepatocellular carcinoma.

    Poulou, Loukia S; Botsa, Evanthia; Thanou, Ioanna; Ziakas, Panayiotis D; Thanos, Loukas

    2015-05-18

    Hepatocellular cancer ranks fifth among cancers and is related to chronic viral hepatitis, alcohol abuse, steatohepatitis and liver autoimmunity. Surgical resection and orthotopic liver transplantation have curative potential, but fewer than 20% of patients are suitable candidates. Interventional treatments are offered to the vast majority of patients. Radiofrequency (RFA) and microwave ablation (MWA) are among the therapeutic modalities, with similar indications which include the presence of up to three lesions, smaller than 3 cm in size, and the absence of extrahepatic disease. The therapeutic effect of both methods relies on thermal injury, but MWA uses an electromagnetic field as opposed to electrical current used in RFA. Unlike MWA, the effect of RFA is partially limited by the heat-sink effect and increased impedance of the ablated tissue. Compared with RFA, MWA attains a more predictable ablation zone, permits simultaneous treatment of multiple lesions, and achieves larger coagulation volumes in a shorter procedural time. Major complications of both methods are comparable and infrequent (approximately 2%-3%), and they include haemorrhage, infection/abscess, visceral organ injury, liver failure, and pneumothorax. RFA may incur the additional complication of skin burns. Nevertheless, there is no compelling evidence for differences in clinical outcomes, including local recurrence rates and survival. PMID:26052394

  11. Recent Advances in Tumor Ablation for Hepatocellular Carcinoma.

    Kang, Tae Wook; Rhim, Hyunchul

    2015-09-01

    Image-guided tumor ablation for early stage hepatocellular carcinoma (HCC) is an accepted non-surgical treatment that provides excellent local tumor control and favorable survival benefit. This review summarizes the recent advances in tumor ablation for HCC. Diagnostic imaging and molecular biology of HCC has recently undergone marked improvements. Second-generation ultrasonography (US) contrast agents, new computed tomography (CT) techniques, and liver-specific contrast agents for magnetic resonance imaging (MRI) have enabled the early detection of smaller and inconspicuous HCC lesions. Various imaging-guidance tools that incorporate imaging-fusion between real-time US and CT/MRI, that are now common for percutaneous tumor ablation, have increased operator confidence in the accurate targeting of technically difficult tumors. In addition to radiofrequency ablation (RFA), various therapeutic modalities including microwave ablation, irreversible electroporation, and high-intensity focused ultrasound ablation have attracted attention as alternative energy sources for effective locoregional treatment of HCC. In addition, combined treatment with RFA and chemoembolization or molecular agents may be able to overcome the limitation of advanced or large tumors. Finally, understanding of the biological mechanisms and advances in therapy associated with tumor ablation will be important for successful tumor control. All these advances in tumor ablation for HCC will result in significant improvement in the prognosis of HCC patients. In this review, we primarily focus on recent advances in molecular tumor biology, diagnosis, imaging-guidance tools, and therapeutic modalities, and refer to the current status and future perspectives for tumor ablation for HCC. PMID:26674766

  12. Excimer laser-ablated plasma atomic spectrometry

    The characterization and evaluation of a new kind of excimer laser-ablated plasma and applications for direct spectrochemical analysis were investigated through time- and space-resolved spectroscopy. The shape, size, emission spectra, and excitation temperatures of the plasma are largely department on the atmospheric surroundings, the ambient gas composition, the pressure, and laser energy. Spatial discrimination may be desirable to increase the line-to-background (L/B) ratio in atomic emission spectroscopy. A direct spectrochemical analytical method for solid samples with good linearity was developed using the excimer laser-AES. The sensitivity of the analytical signal varied depending on the chemical matrix of the solid samples. A typical detection limit for potassium in a glass matrix was 0.13 μg/g.

  13. Transurethral microwave needle ablation for bladder cancer

    2001-01-01

    @@To investigate the role of transurethral microwave needle ablation (TUMWNA) in the management of bladder cancer,TUMWNA was carried out in 24 patients with bladder cancer since 1989. From January 1989 to December 1997, 24 patients with bladder cancer were treated with TUMWNA. The 15 men and 9 women were 42 to 67 years old (mean, 58). There were 18 cases with a single tumor and 6 with multiple tumors (4 with 2 tumors, 1 with 3 and 1 with 4). Tumor diameter ranged from 0.3 to 2.5 cm. The lesions grew in different bladder regions: 13 tumors arose from the fundus, 3 tumors from the dome, 9 from the lateral wall, 5 from the anterior wall, 1 from the triangle region and 2 tumors were situated in the obturator nerve reflex sensitive region.

  14. Polarization of plastic targets by laser ablation

    Giuffreda, E.; Delle Side, D.; Krasa, J.; Nassisi, V.

    2016-05-01

    Charge separation in plasmas produced on plastic targets by low laser irradiance, structure of the ion front, and the current of fast electrons expanding into the vacuum chamber ahead of ions are characterized. Of particular interest is the negative current flowing through the plastic targets to the grounded vacuum chamber during the period of laser-target interaction. The subsequent multi - peaked structure of positive target current is correlated with occurrence of double sheet layers. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer KrF laser. The experimental setting allowing the target current observation is discussed.

  15. Intrafetal alcohol ablation of an acardiac twin

    Zahar Azuar Zakaria

    2016-07-01

    Full Text Available The twin reverse arterial perfusion (TRAP sequence is a rare but serious complication of mono-chorionic multiple pregnancies in which the affected twin is reversely perfused from the healthy co-twin. The unaffected twin is at risk of cardiac de-compensation or complication related to polyhydramnios, preterm pre-labour rupture of membrane and preterm delivery. When the risk to the healthy fetus increases significantly, the management is to occlude the circulation to the acardiac twin. Here we report a case successfully managed with intra-fetal alcohol ablation at the mid-trimester. [Int J Reprod Contracept Obstet Gynecol 2016; 5(7.000: 2421-2424

  16. LAPAROSCOPIC NEPHRECTOMY USING RADIOFREQUENCY THERMAL ABLATION

    B. Ya. Alekseev

    2014-08-01

    Full Text Available The wide use of current diagnostic techniques, such as ultrasound study, computed tomography, and magnetic resonance imaging, has led to significantly increased detection rates for disease in its early stages. This gave rise to a change in the standards for the treatment of locally advanced renal cell carcinoma (RCC. Laparoscopic nephrectomy (LN has recently become the standard treatment of locally advanced RCC in the clinics having much experience with laparoscopic surgery. The chief drawback of LN is difficulties in maintaining intraoperative hemostasis and a need for creating renal tissue ischemia. The paper gives the intermediate results of application of the new procedure of LN using radiofrequency thermal ablation in patients with non-ischemic early-stage RCC.

  17. Surgical ablation devices for atrial fibrillation.

    Lall, Shelly C; Damiano, Ralph J

    2007-12-01

    The introduction of ablation technology has revolutionized the surgical treatment of atrial fibrillation (AF). It has greatly simplified surgical approaches and has significantly increased the number of procedures being performed. Various energy sources have been used clinically, including cryoablation, radiofrequency, microwave, laser, and high-frequency ultrasound. The goal of these devices is to create conduction block to either block activation wavefronts or to isolate the triggers of AF. All present devices have been shown to have clinical efficacy in some patients. The devices each have their unique advantages and disadvantages. It is important that surgeons develop accurate dose-response curves for new devices in clinically relevant models on both the arrested and beating heart. This will allow the appropriate use of technology to facilitate AF surgery. PMID:18175210

  18. Enhanced coupling of optical energy during liquid-confined metal ablation

    Kang, Hyun Wook, E-mail: wkang@pknu.ac.kr [Department of Biomedical Engineering, Pukyong National University, Busan, South Korea and Center for Marine-integrated Biomedical Technology (MIBT), Pukyong National University, Busan (Korea, Republic of); Welch, Ashley J. [Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, 78712 (United States)

    2015-10-21

    Liquid-confined laser ablation was investigated with various metals of indium, aluminum, and nickel. Ablation threshold and rate were characterized in terms of surface deformation, transient acoustic responses, and plasma emissions. The surface condition affected the degree of ablation dynamics due to variations in reflectance. The liquid confinement yielded up to an order of larger ablation crater along with stronger acoustic transients than dry ablation. Enhanced ablation performance resulted possibly from effective coupling of optical energy at the interface during explosive vaporization, plasma confinement, and cavitation. The deposition of a liquid layer can induce more efficient ablation for laser metal processing.

  19. Enhanced coupling of optical energy during liquid-confined metal ablation

    Liquid-confined laser ablation was investigated with various metals of indium, aluminum, and nickel. Ablation threshold and rate were characterized in terms of surface deformation, transient acoustic responses, and plasma emissions. The surface condition affected the degree of ablation dynamics due to variations in reflectance. The liquid confinement yielded up to an order of larger ablation crater along with stronger acoustic transients than dry ablation. Enhanced ablation performance resulted possibly from effective coupling of optical energy at the interface during explosive vaporization, plasma confinement, and cavitation. The deposition of a liquid layer can induce more efficient ablation for laser metal processing

  20. Solar Wind Ablation of Terrestrial Planet Atmospheres

    Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

    2009-01-01

    Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

  1. Ablation dynamics in laser sclerotomy ab externo

    Brinkmann, Ralf; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

    1996-01-01

    Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

  2. Deflection of uncooperative targets using laser ablation

    Thiry, Nicolas; Vasile, Massimiliano

    2015-09-01

    Owing to their ability to move a target in space without requiring propellant, laser-based deflection methods have gained attention among the research community in the recent years. With laser ablation, the vaporized material is used to push the target itself allowing for a significant reduction in the mass requirement for a space mission. Specifically, this paper addresses two important issues which are thought to limit seriously the potential efficiency of a laser-deflection method: the impact of the tumbling motion of the target as well as the impact of the finite thickness of the material ablated in the case of a space debris. In this paper, we developed a steady-state analytical model based on energetic considerations in order to predict the efficiency range theoretically allowed by a laser deflection system in absence of the two aforementioned issues. A numerical model was then implemented to solve the transient heat equation in presence of vaporization and melting and account for the tumbling rate of the target. This model was also translated to the case where the target is a space debris by considering material properties of an aluminium 6061-T6 alloy and adapting at every time-step the size of the computational domain along with the recession speed of the interface in order to account for the finite thickness of the debris component. The comparison between the numerical results and the analytical predictions allow us to draw interesting conclusions regarding the momentum coupling achievable by a given laser deflection system both for asteroids and space debris in function of the flux, the rotation rate of the target and its material properties. In the last section of this paper, we show how a reasonably small spacecraft could deflect a 56m asteroid with a laser system requiring less than 5kW of input power.

  3. Displacement of the posterior part of the eyeball in myopia

    The principal aim of this study was to investigate displacement of the posterior part of the eyeball within the muscle cone in myopic eyes, particularly in moderately myopic subjects as well as in high myopes. Secondly, the correlation of the amount of displacement and the outer axial length of the globe was studied. The direction of displacement was also examined to clarify whether the eyeball tends to shift toward a certain direction. Seven patients with moderate myopia (moderate myopia group), fifteen patients with high myopia without esotropia (high myopia group), five patients with high myopia and esotropia (myopic esotropia group), and twenty-two controls (control group) were examined. Using magnetic resonance imaging, the outer axial length and the displacement of the posterior portion of the eyeball in the muscle cone were measured. In order to eliminate interindividual differences in the facial configuration, the coronal scanning was done perpendicularly to the orbital axis. The displacement was measured in a plane 4 mm anterior to the globe-optic nerve junction. The displacement was represented by the distance and direction of the globe center from the center of the muscle cone. In the moderate myopia group, there was no displacement of the posterior part of the eyeball in the muscle cone. It was the same as in the control group. But among the three groups, the displacement (mean±standard deviation) was significantly greater in the myopic esotropia group (1.53±0.49 mm) and the high myopia group (0.94±0.52 mm) than in the control group (0.11±0.18 mm) (one way ANOVA and multiple comparison). The outer axial length and the distance of the displacement in all cases was significantly correlated (r=0.87, p=0.01). Moreover, the posterior part of the eyeball of the myopic esotropia group and the high myopia group was displaced superiorly and temporally. The posterior part of the eyeball of myopic eyes was displaced superotemporally in the muscle cone

  4. MRI of radial displacement of the meniscus in the knee

    Objective: To describe the phenomenon of radial displacement of the meniscus of the knees in the study population with MR imaging, and to establish MRI diagnostic criteria for radial displacement of the meniscus and displacement index. Methods: MR signs of radial displacement of the meniscus were evaluated retrospectively in 398 patients with knee symptoms who were examined with non- weight bearing MR images from Jan. 2000 to Feb. 2004. The patients younger than 18 years old, with joint effusion or serious arthropathy were excluded and 312 patients were eligible to be enrolled in this study. The criterion for radial displacement of the meniscus was defined as the location of the edge of meniscal body beyond the femoral and tibial outer border line. A displacement index, defined as the ratio of meniscal overhang to meniscal width, was used to quantify meniscal displacement. Results: The prevalence of radial displacement of the meniscus was 16.7% (52/312) and 13.9% (21/151) in right knee and 19.3% (31/161 )in left knee, respectively. There was no significant difference between left and right knee (χ2=1.60, P>0.05) and the ratio between medial and lateral meniscus was 7.8:1. The average displacement index was 0.54±0.24. The displacement indices were significant higher in older group (F=3.63, P<0.05). The incidence and indices of radial displacement of the meniscus for patients under or above 50 year older were 12.0%(17/142), 0.46±0.22 and 20.6% (35/170), 0.64±0.20, respectively. Difference was highly significant (t=0.84, P<0.01). Conclusion: It was concluded that radial displacement of the meniscus in knees was not a rare finding with MR imaging in patients with knee symptoms. The incidence increased in older age group. Further investigations were recommended to understand the etiology and clinical significance of the phenomenon of radial displacement of the meniscus. (authors)

  5. Control of laser-ablation plasma potential with external electrodes

    The potential of a laser-ablation plasma was controlled stably up to +2 kV by using external ring electrodes. A stable electron sheath was formed between the plasma and the external electrodes by placing the ring electrodes away from the boundary of the drifting plasma. The plasma kept the potential for a few μs regardless of the flux change of the ablation plasma. We also found that the plasma potential changed with the expansion angle of the plasma from the target. By changing the distance between the plasma boundary and the external electrodes, we succeeded in controlling the potential of laser-ablation plasma

  6. Ablation of film stacks in solar cell fabrication processes

    Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

    2013-04-02

    A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

  7. Synchrotron radiation photoionization mass spectrometry of laser ablated species

    Alvarez Ruiz, J., E-mail: j.alvarez@iqfr.csic.e [Instituto de Quimica Fisica Rocasolano, CSIC, 28006 Madrid (Spain); Casu, A. [University of Cagliari, 09042 Monserrato (Italy); Coreno, M. [CNR-IMIP, c/o Lab. Elettra Trieste, 00016 Montelibretti (Italy); Simone, M. de [CNR-INFM, Laboratorio Nazionale TASC, 34149 Trieste (Italy); Hoyos Campo, L.M.; Juarez-Reyes, A.M. [ICF-UNAM Cuernavaca (Mexico); Kivimaeki, A. [CNR-INFM, Laboratorio Nazionale TASC, 34149 Trieste (Italy); Orlando, S. [CNR-IMIP, c/o Lab. Elettra Trieste, 00016 Montelibretti (Italy); Sanz, M. [Instituto de Quimica Fisica Rocasolano, CSIC, 28006 Madrid (Spain); Spezzani, C. [Sincrotrone Trieste, 34149 Trieste (Italy); Stankiewicz, M. [Jagiellonian University, 30-059 Krakow (Poland); Trucchi, D.M. [CNR - ISC, 00016 Montelibretti (Italy)

    2010-02-15

    The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral S{sub n} clusters (n = 1-8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation-synchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radicals.

  8. Synchrotron radiation photoionization mass spectrometry of laser ablated species

    The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1-8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation-synchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radicals.

  9. Micrometeorological processes driving snow ablation in an Alpine catchment

    R. Mott

    2011-11-01

    Full Text Available Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micro-meteorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological boundary-layer model (Advanced Regional Prediction System with a fully distributed energy balance model (Alpine3D. Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modeled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances of about 4–6 m. Measurements suggest that mean wind velocities of about 5 m s−1 are required for advective heat transport to increase snow ablation over a long fetch distance of about 20 m. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value of approximately 0.6. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is low. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover

  10. Mapping and Surgical Ablation of Focal Epicardial Left Ventricular Tachycardia

    Arif Elvan

    2011-01-01

    Full Text Available We describe a technical challenge in a 17-year-old patient with incessant epicardial focal ventricular arrhythmia and diminished LV function. Failure of ablation at the earliest activated endocardial site during ectopy suggested an epicardial origin, which was supported by specific electrocardiographic criteria. Epicardial ablation was not possible due to the localization of the origin of the ventricular tachycardia adjacent to the phrenic nerve. Minimal invasive surgical multielectrode high-density epicardial mapping was performed to localize the arrhythmia focus. Epicardial surgical RF ablation resulted in the termination of ventricular ectopy. After 2 years, the patient is still free from arrhythmias.

  11. Endoscopic ultrasound-guided radiofrequency ablation of the pancreas

    Silviu, Ungureanu Bogdan; Daniel, Pirici; Claudiu, Mărgăritescu;

    2015-01-01

    ultrasound (EUS)-guided radiofrequency ablation (RFA) probe through a 19G needle in order to achieve a desirable necrosis area in the pancreas. Radiofrequency ablation of the head of the pancreas was performed on 10 Yorkshire pigs with a weight between 25 kg and 35 kg and a length of 40-70 cm. Using an EUS...... analysis revealed increased values of amylase, alkaline phosphatase, and gamma-glutamyl transpeptidase on the 3rd day but a decrease on the 5th day. After necropsy and isolation of the pancreas, the ablated area was easily found, describing a solid necrosis. The pathological examination revealed...

  12. Ablative Thermal Response Analysis Using the Finite Element Method

    Dec John A.; Braun, Robert D.

    2009-01-01

    A review of the classic techniques used to solve ablative thermal response problems is presented. The advantages and disadvantages of both the finite element and finite difference methods are described. As a first step in developing a three dimensional finite element based ablative thermal response capability, a one dimensional computer tool has been developed. The finite element method is used to discretize the governing differential equations and Galerkin's method of weighted residuals is used to derive the element equations. A code to code comparison between the current 1-D tool and the 1-D Fully Implicit Ablation and Thermal Response Program (FIAT) has been performed.

  13. Near-field mapping by laser ablation of PMMA coatings

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana; Kjelstrup-Hansen, Jakob; Rubahn, Horst-Günter

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating subdiffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy...... the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....

  14. Phrenic Nerve Injury After Catheter Ablation of Atrial Fibrillation

    2007-01-01

    Phrenic Nerve Injury (PNI) has been well studied by cardiac surgeons. More recently it has been recognized as a potential complication of catheter ablation with a prevalence of 0.11 to 0.48 % after atrial fibrillation (AF) ablation. This review will focus on PNI after AF ablation Anatomical studies have shown a close relationship between the right phrenic nerve and it's proximity to the superior vena cava (SVC), and the antero-inferior part of the right superior pulmonary vein (RSPV). In addi...

  15. Overview of the CHarring Ablator Response (CHAR) Code

    Amar, Adam J.; Oliver, A. Brandon; Kirk, Benjamin S.; Salazar, Giovanni; Droba, Justin

    2016-01-01

    An overview of the capabilities of the CHarring Ablator Response (CHAR) code is presented. CHAR is a one-, two-, and three-dimensional unstructured continuous Galerkin finite-element heat conduction and ablation solver with both direct and inverse modes. Additionally, CHAR includes a coupled linear thermoelastic solver for determination of internal stresses induced from the temperature field and surface loading. Background on the development process, governing equations, material models, discretization techniques, and numerical methods is provided. Special focus is put on the available boundary conditions including thermochemical ablation and contact interfaces, and example simulations are included. Finally, a discussion of ongoing development efforts is presented.

  16. CT imaging of complications of catheter ablation for atrial fibrillation

    The complication rate following radiofrequency catheter ablation for atrial fibrillation is low (<5%). Complications include pericardial effusion, cardiac tamponade, pulmonary vein stenosis, oesophageal ulceration or perforation, atrio-oesophageal fistula formation, stroke/transient ischaemic attack, phrenic nerve injury, haematoma at the puncture site, and femoral arteriovenous fistula. Among available imaging tools, computed tomography (CT) can be very useful in diagnosing complications of the procedure, particularly in the subacute and delayed stages after ablation. This review illustrates CT imaging of several of the common and uncommon complications of radiofrequency catheter ablation

  17. Percutaneous radiofrequency thermal ablation of lung VX2 tumors in a rabbit model: evaluation with helical CT findings for the complete and partal ablation

    Jin, Gong Yong; Han, Young Min; Lim, Yeong Su; Jang, Kyu Yun; Lee, Sang Yong; Chung, Gyung Ho [School of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

    2004-05-01

    To evaluate the radiologic findings for complete and partial ablation after percutaneous CT-guided transthoracic radiofrequency ablation (RFA) of lung VX2 tumor implanted in rabbits. Thirteen rabbits with successfully implanted lung VX2 were used. Three rabbits as controls did not receive RFA while the other ten rabbits underwent RFA; 5 complete and 5 partial. RFA was performed using an internally cooled, 17-gauge electrode (Radionics, Burlington, MA) with a 1-cm active tip under CT guidance. Postprocedural CT was performed within 3 days, and we analyzed the ablated size, enhancement pattern, shape, margin, and complications of the complete and partial ablation groups. Rabbits were sacrificed after postprocedural CT with an overdose of ketamine, and pathologic findings of the ablated groups were compared with those of the control group. The size of the ablated lesions and the enhancement pattern differed between the completely and partially ablated groups on chest CT. The size of the ablated lesions was increased by 47.1% in the completely ablated group and by 2.1% in the partially ablated group. In the completely ablated group, VX2 tumor showed absolutely no enhancement, whereas only ablated pulmonary parenchyma outside VX2 showed mild enhancement on enhanced CT. In the partial ablated group, a part of VX2 became strongly enhanced on enhanced CT. On microscopic examination, the completely ablated group demonstrated that a viable tumor cell was not visible. In the partially ablated group, however, a viable tumor cell within the surrounding fibrous capsule on the peripheral area of the VX2 was observed. The important CT findings for evaluation of complete and partial RFA are the ablated size and enhancement pattern of the ablated lesion.

  18. The role of environmental degradation in population displacement.

    Lonergan, S

    1998-01-01

    This article answers a series of questions about the role of environmental degradation in population displacement, refugee movement, and migration. The environment tends not to be included in the reasons for migration. Roger's indicators of migration potential include population growth, economic restructuring, increased economic disparities, and increased refugee flows. Myers (1993) estimated that international displacement and internal displacement may amount to about 25 million and may rise to 150 million by 2050. The role of the environment in displacement must be examined in the broader political and cultural context. Definitions of environmental refugees are ambiguous and inconsistent, and research has not answered why people continue to move to Mexico City and Chongqing, China, which both have very high levels of pollution. El-Hinnawi (1985) defined 3 groups of environmental refugees: those displaced due to natural disasters; those displaced due to permanent habitat changes; and those displaced who migrated from areas that cannot support their basic needs and who desire an improved quality of life. Lonergan (1994) identified environmental stresses as natural disasters, cumulative or slow-onset changes, accidental disruptions or industrial accidents, development projects, and conflict and warfare. These 5 causes must be treated separately and not lumped together as environmental degradation. Shoreline erosion, coastal flooding, and agricultural disruption associated with climate change may increase migration. Global measures must address world poverty and promote sustainable development. PMID:12321719

  19. Measurement of chest wall displacement based on terahertz wave

    Li, Hui; Lv, Hao; Jiao, Teng; Lu, Guohua; Li, Sheng; Li, Zhao; Liu, Miao; Jing, Xijing; Wang, Jianqi

    2015-02-01

    Measurement of chest wall displacement is an important approach for measuring mechanics of chest wall, which has considerable significance for assessing respiratory system and diagnosing pulmonary diseases. However, existing optical methods for measuring chest wall displacement are inconvenient for some specific patients such as the female patients and the patients with bandaged chest. In this letter, we proposed a method for measuring chest wall displacement based on terahertz wave and established corresponding mathematic model and set up a terahertz measurement system. The main advantages of this method are that it can measure the chest wall displacement of the subjects without taking off clothes or arranging any markers. To validate this method and assess the performance of the terahertz system, in vitro, the displacement of a water module driven by a linear guide rail was measured by the terahertz system and compared with the actual displacement of the water module. The results showed that the waveforms measured with two methods have a good agreement, and the relative error is less than 5% and sufficiently good for measurement demands. In vivo, the synchronous experiment was performed on five human volunteers with the terahertz system and a respiratory belt transducer. The results demonstrate that this method has good performance and promising prospects for measuring chest wall displacement.

  20. The Effect of Basepair Mismatch on DNA Strand Displacement.

    Broadwater, D W Bo; Kim, Harold D

    2016-04-12

    DNA strand displacement is a key reaction in DNA homologous recombination and DNA mismatch repair and is also heavily utilized in DNA-based computation and locomotion. Despite its ubiquity in science and engineering, sequence-dependent effects of displacement kinetics have not been extensively characterized. Here, we measured toehold-mediated strand displacement kinetics using single-molecule fluorescence in the presence of a single basepair mismatch. The apparent displacement rate varied significantly when the mismatch was introduced in the invading DNA strand. The rate generally decreased as the mismatch in the invader was encountered earlier in displacement. Our data indicate that a single base pair mismatch in the invader stalls branch migration and displacement occurs via direct dissociation of the destabilized incumbent strand from the substrate strand. We combined both branch migration and direct dissociation into a model, which we term the concurrent displacement model, and used the first passage time approach to quantitatively explain the salient features of the observed relationship. We also introduce the concept of splitting probabilities to justify that the concurrent model can be simplified into a three-step sequential model in the presence of an invader mismatch. We expect our model to become a powerful tool to design DNA-based reaction schemes with broad functionality. PMID:27074674

  1. A method to calculate displacement factors using SVM

    Li Peixian; Tan Zhixiang; Yan Lili; Deng Kazhong

    2011-01-01

    In order to improve the precision of mining subsidence prediction,a mathematical model using Support Vector Machine (SVM) was established to calculate the displacement factor.The study is based on a comprehensive analysis of factors affecting the displacement factor,such as mechanical properties of the cover rock,the ratio of mining depth to seam thickness,dip angle of the coal seam and the thickness of loose layer.Data of 63 typical observation stations were used as a training and testing sample set.A SVM regression model of the displacement factor and the factors affecting it was established with a kernel function,an insensitive loss factor and a properly selected penalty factor.Given an accurate calculation algorithm for testing and analysis,the results show that an SVM regression model can calculate displacement factor precisely and reliable precision can be obtained which meets engineering requirements.The experimental results show that the method to calculation of the displacement factor,based on the SVM method,is feasible.The many factors affecting the displacement factor can be considered with this method.The research provides an efficient and accurate approach for the calculation of displacement in mining subsidence prediction.

  2. Novel energy modalities for catheter ablation of cardiac arrhythmias : Pitfalls and possibilities of potent power sources

    Neven, K.G.E.J.

    2014-01-01

    The acceptance of catheter ablation as treatment for cardiac arrhythmias is amongst others dependent on its success rate, a high initial success rate will increase physician and patient acceptance. One of the reasons why recurrence of arrhythmia after ablation is substantial is non-transmurality of ablation lesions. Transmurality is essential for conduction block and is depending on many factors, such as tissue ablation duration, thickness of the cardiac wall, ablation technique used, cathete...

  3. A Study of Horizontal Displacement of Laterally Loaded Piles

    Aram M. Raheem

    2013-05-01

    Full Text Available  A theoretical approach is used to analyze single pile and pile in group under lateral loading using two programs. The first one used the finite element method for single pile depending on plain strain condition while the second one used the characteristic load method for pile in group. Horizontal displacement for pile in group is measured while both horizontal displacement and shear stress for single pile are measured. A comparison between the results of horizontal displacement for both single pile and pile in group with the actual practical values are produced and shows a good agreement.

  4. Human response to ductless personalized ventilation coupled with displacement ventilation

    Dalewski, Mariusz; Veselý, Michal; Melikov, Arsen K.

    A human subject experiment was carried out to investigate the extent to which ductless personalized ventilation (DPV) in conjunction with displacement ventilation can improve perceived air quality (PAQ) and thermal comfort at elevated room air temperature in comparison with displacement ventilation......). During one hour exposure participants answered questionnaires regarding PAQ and thermal comfort. PAQ was significantly better with DPV than without DPV at the same background conditions. Thermal comfort improved when DPV was used. Combining DPV with displacement ventilation showed the potential for...... improving PAQ and thermal comfort when room air temperature is above the comfortable temperature range....

  5. Helium vs. Proton Induced Displacement Damage in Electronic Materials

    Ringo, Sawnese; Barghouty, A. F.

    2010-01-01

    In this project, the specific effects of displacement damage due to the passage of protons and helium nuclei on some typical electronic materials will be evaluated and contrasted. As the electronic material absorbs the energetic proton and helium momentum, degradation of performance occurs, eventually leading to overall failure. Helium nuclei traveling at the same speed as protons are expected to impart more to the material displacement damage; due to the larger mass, and thus momentum, of helium nuclei compared to protons. Damage due to displacement of atoms in their crystalline structure can change the physical properties and hence performance of the electronic materials.

  6. The effect of Coulombic friction on spatial displacement statistics

    Menzel, Andreas M

    2010-01-01

    The phenomenon of Coulombic friction enters the stochastic description of dry friction between two solids and the statistic characterization of vibrating granular media. Here we analyze the corresponding Fokker-Planck equation including both velocity and spatial components, exhibiting a formal connection to a quantum mechanical harmonic oscillator in the presence of a delta potential. Numerical solutions for the resulting spatial displacement statistics show a crossover from exponential to Gaussian displacement statistics. We identify a transient intermediate regime that exhibits multiscaling properties arising from the contribution of Coulombic friction. These results are relevant to recent experimental studies of the displacement of colloidal particles along bilayer membrane tubes.

  7. Measurement of local relative displacements in large structures

    Tesauro, Angelo; Eder, Martin Alexander; Nielsen, Magda

    2014-01-01

    and capable of measuring 3D local displacements with a high degree of accuracy. In this article, the technique is used to measure local deformations in the vicinity of the adhesive trailing edge joint of a wind turbine rotor blade. The SDMS results correspond well with another independent measurement...... particular. The measurement of small local relative displacements in structures subjected to large global deformations is complex and hardly feasible with conventional measurement methods. Therefore, a Small Displacement Measurement System (SDMS) has been devised. The SDMS is based on stereo photogrammetry...

  8. Limitation for performing ultrasound-guided radiofrequency ablation of small renal masses

    Park, Byung Kwan, E-mail: rapark@skku.ed [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Zip code: 135-710, Seoul (Korea, Republic of); Kim, Chan Kyo [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Zip code: 135-710, Seoul (Korea, Republic of); Choi, Han Yong; Lee, Hyun Moo; Jeon, Seong Soo; Seo, Seong Il; Han, Deok Hyun [Department of Urology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2010-08-15

    Purpose: To evaluate which factor is involved in limiting ultrasound (US)-guided radiofrequency (RF) ablation of small renal masses. Materials and methods: Twenty-five patients with 31 renal masses underwent image-guided RF ablation. If a lesion was visible on US, US-guided RF ablation was performed. If a lesion was invisible on US or if the lesion was incompletely ablated or recurred following US-guided RF ablation, CT-guided RF ablation was performed. We analyzed the various factors which were involved in US-guided RF ablation. Results: Of 31 masses, thirteen were US-visible lesions and underwent US-guided RF ablation whereas thirteen were US-invisible lesions and thus underwent CT-guided RF ablation. The remaining five lesions were US-visible but needed additional CT-guided RF ablation, due to incomplete ablation (n = 4) or recurrence (n = 1); these renal masses (3.1 {+-} 1.0 cm) were significantly larger than those (1.8 {+-} 0.6 cm) ablated with US alone (p < 0.05). Steam bubbles (4.4 cm {+-} 0.7 cm) of the masses requiring additional CT-guided RF ablation were significantly larger than those (2.9 cm {+-} 0.7 cm) of the tumors completely ablated with US alone in size (p < 0.05). Conclusions: US-invisibility, lesion size, and steam bubbles may limit to perform US-guided RF ablation of small renal masses.

  9. Intra-cardiac echocardiography in alcohol septal ablation

    Cooper, Robert M; Shahzad, Adeel; Newton, James;

    2015-01-01

    Alcohol septal ablation (ASA) in hypertrophic obstructive cardiomyopathy reduces left ventricular outflow tract gradients. A third of patients do not respond; inaccurate localisation of the iatrogenic infarct can be responsible. Transthoracic echocardiography (TTE) using myocardial contrast can be...

  10. Efficiency of Planetesimal Ablation in Giant Planetary Envelopes

    Pinhas, Arazi; Clarke, Cathie

    2016-01-01

    Observations of exoplanetary spectra are leading to unprecedented constraints on their atmospheric elemental abundances, particularly O/H, C/H, and C/O ratios. Recent studies suggest that elemental ratios could provide important constraints on formation and migration mechanisms of giant exoplanets. A fundamental assumption in such studies is that the chemical composition of the planetary envelope represents the sum-total of compositions of the accreted gas and solids during the formation history of the planet. We investigate the efficiency with which accreted planetesimals ablate in a giant planetary envelope thereby contributing to its composition rather than sinking to the core. From considerations of aerodynamic drag causing `frictional ablation' and the envelope temperature structure causing `thermal ablation', we compute mass ablations for impacting planetesimals of radii 30 m to 1 km for different compositions (ice to iron) and a wide range of velocities and impact angles, assuming spherical symmetry. I...

  11. Non-ablative controlled local hyperthermia for common warts

    GAO Xing-hua; GAO Dan; SUN Xiu-ping; HUO Wei; HONG Yu-xiao; LI Xiao-dong; WANG Xiao-qin; QI Rui-qun; ZHANG Li; GU Xiao-chuan; CHEN Hong-duo

    2009-01-01

    th warts might resolve spontaneously within 2 years,4 while in some patients warts persist for years.3 A cellular immune response is essential for the clearance of HPV.6,7 Treatment modalities are usually ablative.

  12. Radiofrequency ablation for neuroendocrine liver metastases: a systematic review.

    Mohan, Helen; Nicholson, Patrick; Winter, Des C; O'Shea, Donal; O'Toole, Dermot; Geoghegan, Justin; Maguire, Donal; Hoti, Emir; Traynor, Oscar; Cantwell, Colin P

    2015-07-01

    To determine the efficacy of radiofrequency (RF) ablation in neuroendocrine tumor (NET) liver metastases. A systematic review was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eight studies were included (N = 301). Twenty-six percent of RF ablation procedures were percutaneous (n = 156), with the remainder conducted at surgery. Forty-eight percent of patients had a concomitant liver resection. Fifty-four percent of patients presented with symptoms, with 92% reporting symptom improvement following RF ablation (alone or in combination with surgery). The median duration of symptom improvement was 14-27 months. However, recurrence was common (63%-87%). RF ablation can provide symptomatic relief in NET liver metastases alone or in combination with surgery. PMID:25840836

  13. Morphology Characterization of Uranium Particles From Laser Ablated Uranium Materials

    2011-01-01

    In the study, metallic uranium and uranium dioxide material were ablated by laser beam in order to simulate the process of forming the uranium particles in pyrochemical process. The morphology characteristic of uranium particles and the surface of

  14. Collateral damage from Catheter Ablation of Atrial Fibrillation

    Wanwarang Wongcharoen, MD

    2013-04-01

    Full Text Available Atrial fibrillation (AF is the most common sustained arrhythmia, contributing to a significant morbidity and mortality. Catheter ablation of the pulmonary veins (PVs and left atrium (LA has been shown to be an effective strategy for the treatment of symptomatic AF. Regardless of technological advances and technique improvement, catheter ablation for AF remains a highly complex procedure and the risk of procedural complications is not negligible. The major complications have been reported to occur in up to 5.2% of procedures. A systematic investigation among 32,569 patients undergoing catheter ablation for AF has demonstrated that mortality is around 0.1%. Nevertheless, the true prevalence of complications is possibly underestimated in retrospective surveys because of recollection bias and other factors. This article will focus on the management of serious complications of catheter AF ablation including PV stenosis, atrioesophageal fistula, cardiac tamponade, stroke and thromboembolic complication

  15. Laser ablation in analytical chemistry-a review.

    Russo, Richard E; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S

    2002-05-24

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas. PMID:18968642

  16. Preparation of Nanostructurated Materials by ArF Laser Ablation

    Koštejn, Martin; Fajgar, Radek; Tomovska, R.; Blazevska-Gilev, J.

    -: -, 2014, s. 243. ISBN N. [International Conference on Nanosciences & Nanotechnologie (NN13) /10./. Thessaloniki (GR), 09.07.2014-12.07.2014] Institutional support: RVO:67985858 Keywords : laser ablation * electron diffraction * spectroscopy Subject RIV: CH - Nuclear ; Quantum Chemistry

  17. HYDRA: Macroscopic 3D Approach of Light Weight Ablator

    Pinaud, G.; Barcena, J.; Bouilly, J.-M.; Leroy, V.; Fischer, Wpp.; Massuti, T.

    2014-06-01

    The HYDRA project is an European funded program that aims at developing novel solution in term of TPS associated to a demonstration of Technology Readiness Level (TRL) 4. We describe modelling activities (radiation/ablation) compared to plasma test.

  18. Computer-aided hepatic tumour ablation requirements and preliminary results

    Voirin, D; Amavizca, M; Letoublon, C; Troccaz, J; Voirin, David; Payan, Yohan; Amavizca, Miriam; Letoublon, Christian; Troccaz, Jocelyne

    2002-01-01

    Surgical resection of hepatic tumours is not always possible, since it depends on different factors, among which their location inside the liver functional segments. Alternative techniques consist in local use of chemical or physical agents to destroy the tumour. Radio frequency and cryosurgical ablations are examples of such alternative techniques that may be performed percutaneously. This requires a precise localisation of the tumour placement during ablation. Computer-assisted surgery tools may be used in conjunction with these new ablation techniques to improve the therapeutic efficiency, whilst they benefit from minimal invasiveness. This paper introduces the principles of a system for computer-assisted hepatic tumour ablation and describes preliminary experiments focusing on data registration evaluation. To keep close to conventional protocols, we consider registration of pre-operative CT or MRI data to intra-operative echographic data.

  19. AF Termination: the Holy Grail of Persistent AF Ablation?

    Dennis H. Lau, MBBS

    2010-06-01

    Full Text Available The optimal catheter ablation approach for longstanding persistent atrial fibrillation (AF remains elusive despite significant advances made in our understanding of this arrhythmia. A recent systematic review highlighted the significant variation in procedural success rate both within and between techniques, necessitating repeat ablation procedures and anti-arrhythmic drugs to achieve improved outcomes in those with long-standing persistent AF.1 Indeed, current expert consensus statement recommended ablation beyond ostial pulmonary vein isolation for these patients.2 Despite incorporating various substrate modification techniques which commonly include linear lesions and targeting of complex fractionated electrograms, the reported success rates from various laboratories are still below par to those in paroxysmal AF patients.1 Perhaps the often dilated and chronically remodeled atria in longstanding persistent AF patients harbor complex structural substrates capable of maintaining the arrhythmia beyond amelioration even with extensive catheter ablation in some. Certainly, this reflects our incomplete understanding of the complex mechanisms underlying this arrhythmia.

  20. Role of shielding in modelling cryogenic deuterium pellet ablation

    For the better characterization of pellet ablation, the numerical LLP code has been enhanced by combining two relevant shielding mechanisms: that of the spherically expanding neutral cloud surrounding the pellet and that of the field elongated ionized material forming a channel flow. In contrast to our expectation the presence of the channel flow can increase the ablation rate although it reduces the heat flux travelling through it. The contribution of the different shielding effect in the ablation process is analysed for several pellet and plasma parameters and an ablation rate scaling is presented based on simple regression in the ASDEX Upgrade pellet and plasma parameter range. Finally the simulated results are compared with experimental data from typical ASDEX Upgrade discharges