Laser Energy Sources Research Articles

Analysis of chromatin-nuclear receptor interactions by laser-chromatin immunoprecipitation.

Better defining the dynamics of biomolecular interactions is an important step in understanding molecular biology and cellular processes. DNA-protein interactions, and specifically hormone-triggered DNA-nuclear receptor interactions, are key events which are still poorly understood. To date, the most commonly used approach in studying chromatin interactions is the immunoprecipitation of chemically cross-linked chromatin (ChIP) coupled with single gene or global genomic analyses. Currently, establishing a stable interplay between nucleic acids and proteins (DNA-protein cross-link) is mainly obtained through conventional, diffusion-triggered, chemical methods using formaldehyde. Here we describe an alternative method, called Laser-ChIP (LChIP), for the specific analysis of interactions between chromatin and nuclear receptors driven by a UV laser energy source. Photo-induced cross-linking in LChIP is achieved very rapidly, allowing the study of transient interactions, depending on laser source parameters.

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 μm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were −26.94 1/mm and −28.42 1/mm for the green and red lasers, respectively.

Industrial laser cladding: current state and future

A state-of-the-art and development tendency of the laser surfacing industrial application is reviewed. Laser energy sources, emission transport and focusing systems, coating materials, and laser equipment are considered.

Processing and characterization of aluminum-based nanothermites

During the past several years, a significant effort has been on investigation of reaction front propagation and the rate of energy release in heterogeneous systems consisting of nanopowder reactants. Substantial size reduction of each reactant powder (e.g. from micro- to nano-size) leads to increase of reaction front propagation in some systems under unconfined conditions by approximately two to three order of magnitude. This paper presents key challenges associated with processing and use of nanothermite materials and characterization of nanoreactants. Reaction constants, such as activation energies and frequency factors were determined using DSC technique for several nanothermite systems based on nanosize aluminum and iron oxide, bismuth trioxide, and molybdenum trioxide. Experimental data of ignition delay times for different nanothermite systems using laser energy source were compared well to those predicted by proposed mathematical model.

Epicardial High-intensity Focused Ultrasound Cardiac Ablation for Surgical Treatment of Atrial Fibrillation

The available alternatives to an effective but technically complex Cox maze procedure for surgical treatment of atrial fibrillation include ablation using radiofrequency, microwave, laser, cryotherapy or ultrasound energy sources. The purpose of this study was to evaluate the safety and efficacy profile of high-intensity focused ultrasound cardiac ablation for the surgical treatment of atrial fibrillation. 14 patients underwent epicardial high-intensity focused ultrasound treatment for atrial fibrillation using the Epicor cardiac ablation system between August 2006 and August 2007. The procedure was performed on the beating heart prior to the commencement of cardiopulmonary bypass for concomitant cardiac procedures. Physical examination, electrocardiography and 24-h Holter monitoring were used to determine the postoperative heart rhythm. There were no deaths directly related to the procedure. One patient with myelodysplastic syndrome died of septic complications. Three patients required cardioversion at 1 day, 3- and 4-month intervals postoperatively. The mean follow-up period was 9 months. Currently 10/13 (77%) patients are in sinus rhythm, one patient required insertion of a permanent pacemaker, one patient is in atrial fibrillation and another patient is in atrial flutter. Epicardial high-intensity focused ultrasound ablation is a viable alternative to the Cox maze procedure for the surgical treatment of atrial fibrillation. It is a safe and efficient procedure that does not require cardiopulmonary bypass and may potentially be performed using less invasive surgical techniques.

Abstracts of the Engineering and Urology Society, May 19, 2007, Anaheim, California

Journal of EndourologyVol. 22, No. 1 Letter to the EditorAbstracts of the Engineering and Urology Society, May 19, 2007, Anaheim, CaliforniaPublished Online:22 Jan 2008https://doi.org/10.1089/end.2007.9935AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited byEditorial CommentUrology, Vol. 99Current evidence on lasers in laparoscopy: partial nephrectomy3 July 2014 | World Journal of Urology, Vol. 33, No. 4Laparoscopic Partial Nephrectomy with Diode Laser: A Promising Technique Nikola Knezevic, Tomislav Kulis, Marjan Maric, Marija Topalovic Grkovic, Ivan Krhen, and Zeljko Kastelan10 February 2014 | Photomedicine and Laser Surgery, Vol. 32, No. 2Robotic radical anterior pelvic exenteration: The UCI experience13 December 2010 | Minimally Invasive Therapy & Allied Technologies, Vol. 20, No. 4Alternative Laser Energy Sources: Clinical Implications2 December 2010 Volume 22Issue 1Jan 2008 InformationMary Ann Liebert, Inc.To cite this article:Abstracts of the Engineering and Urology Society, May 19, 2007, Anaheim, California.Journal of Endourology.Jan 2008.159-212.http://doi.org/10.1089/end.2007.9935Published in Volume: 22 Issue 1: January 22, 2008PDF download

Effect of Epicardial Fat on Ablation Performance: A Three-Energy Source Comparison

To investigate the effect of epicardial fat on surgical atrial fibrillation ablation performance using an in vitro model. Two tissue models were employed to investigate standard penetration and maximal lesion depth performance of bipolar radiofrequency (RF), microwave, and laser energy sources. Ventricular veal tissue was utilized in various thicknesses (3 mm, 5 mm, 7 mm, 15 mm). Epicardial fat was modeled by layering porcine fat (1 mm, 2 mm and 4 mm) on moistened tissue. In each group, 8 to 10 lesions were created. Post ablation, tissue samples were sectioned and ablation depth of each myocardial section measured using 1% tetrazolium tetrachloride dye solution. The laser energy source produced nearly 100% transmural lesions in almost all study groups irrespective of myocardium thickness and fat thickness. The microwave device maintained transmurality in all 3-mm and most 5-mm myocardium trials but fell to near zero with all 7-mm myocardium trials. The bipolar RF maintained transmurality only when no fat was applied. In the maximal lesion depth models, the laser was capable of producing lesions >8 mm with no fat and >6 mm with either 2 mm or 4 mm of fat present. The microwave produced lesions in the no fat (>6 mm) and 2-mm (>4 mm) fat group. The bipolar RF produced 83% transmurality with no fat and zero percent transmurality with 2 mm of fat present. Epicardial fat can severely limit transmurality in energy sources that utilize conductive heating. Laser energy was uniformly superior at producing both transmural and deep lesions irrespective of the presence of fat.

Advances in the Treatment of Superficial Venous Insufficiency of the Lower Extremities

Minimally invasive techniques for ablation of incompetent saphenous veins using either radiofrequency or laser energy sources have gained acceptance and are being widely applied today. Tumescent local anesthesia provides protection to tissues surrounding the treated veins and allows the procedures to be done on conscious patients. Results thus far compare favorably with surgical stripping procedures. Efficacy rates and complication rates support these techniques, and patient satisfaction appears high. Microphlebectomy, also minimally invasive, has advantages over direct incisional excision of varicosities. Foam sclerosant injection therapy has been used extensively in Europe and is proving useful in treating refluxing pelvic veins and recurrent varicosities.

Laser Energy Source in Surgical Atrial Fibrillation Ablation: Preclinical Experience

The purpose of this study was to evaluate diffusing tip laser energy in surgical atrial fibrillation ablation using a canine model. This is the first report to describe the pathological and histological findings using a laser energy source. The surgical atrial fibrillation ablation procedure was performed through a left atriotomy; the pulmonary veins were encircled in 16 dogs using a diode laser (980 nm) with a diffusing tip that permits linear ablation perpendicular to the fiber direction. Lesion durations were 45 seconds with a power density of 3.8 or 4.5 W/cm. Six animals were allowed to survive 4 hours after the procedure, with the remainder sacrificed at 1 week (n = 1), 4 weeks (n = 3), and 6 weeks (n = 6). Electrophysiologic effectiveness was judged using unipolar or bipolar pacing from the pulmonary veins after attempting isolation. Hearts were harvested for histologic examination using standard trichrome staining. All animals tolerated the procedure. The animals required an average of 5.6 +/- 0.82 lesions to complete the procedure. All animals had confirmed isolation of the pulmonary veins as judged by unipolar or bipolar pacing, and this isolation persisted in those animals that were allowed to survive. Pathology revealed all lesions to be transmural with an average tissue thickness of 3.62 +/- 1.50 mm (range, 0.95 mm to 7.06 mm). Diffusing tip laser technology reproducibly makes rapid, transmural, and electrophysiologically effective atrial lesions.

Optics in the relativistic regime

The advent of ultraintense laser pulses generated by the technique of chirped pulse amplification (CPA) along with the development of high-fluence laser materials has opened up an entirely new field of optics. The electromagnetic field intensities produced by these techniques, in excess of ${10}^{18}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$, lead to relativistic electron motion in the laser field. The CPA method is reviewed and the future growth of laser technique is discussed, including the prospect of generating the ultimate power of a zettawatt. A number of consequences of relativistic-strength optical fields are surveyed. In contrast to the nonrelativistic regime, these laser fields are capable of moving matter more effectively, including motion in the direction of laser propagation. One of the consequences of this is wakefield generation, a relativistic version of optical rectification, in which longitudinal field effects could be as large as the transverse ones. In addition to this, other effects may occur, including relativistic focusing, relativistic transparency, nonlinear modulation and multiple harmonic generation, and strong coupling to matter and other fields (such as high-frequency radiation). A proper utilization of these phenomena and effects leads to the new technology of relativistic engineering, in which light-matter interactions in the relativistic regime drives the development of laser-driven accelerator science. A number of significant applications are reviewed, including the fast ignition of an inertially confined fusion target by short-pulsed laser energy and potential sources of energetic particles (electrons, protons, other ions, positrons, pions, etc.). The coupling of an intense laser field to matter also has implications for the study of the highest energies in astrophysics, such as ultrahigh-energy cosmic rays, with energies in excess of ${10}^{20}\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The laser fields can be so intense as to make the accelerating field large enough for general relativistic effects (via the equivalence principle) to be examined in the laboratory. It will also enable one to access the nonlinear regime of quantum electrodynamics, where the effects of radiative damping are no longer negligible. Furthermore, when the fields are close to the Schwinger value, the vacuum can behave like a nonlinear medium in much the same way as ordinary dielectric matter expanded to laser radiation in the early days of laser research.

Cascade lasing of molecular HBr in the four micron region pumped by a Nd:YAG laser

Due to a narrow window of high atmospheric transmission near 4 /spl mu/m there is a great deal of interest for a scalable laser energy source in this spectral region. We propose a concept combining the advantages of solid-state and gas laser technology. It takes advantage of a coincidence of a Nd:YAG laser line and an overtone transition of the molecule HBr. Tuning a Q-switched Nd:YAG laser to 1.3391 /spl mu/m allows us to excite the v(0 /spl rarr/ 3), J(4 /spl rarr/ 5) vibrational-rotational transition of HBr. To stabilize the pump frequency, a diode laser locked to this HBr transition seeds the Nd:YAG laser. Once excited, HBr can potentially lase in three subsequent steps to the ground state, two of which were observed experimentally, emitting up to three photons in the 4-/spl mu/m region. We present theoretical and experimental results demonstrating the operational principle of this laser system. The comparison of experiment and theory suggests: 1) that intracavity CO/sub 2/ can force the system to lase on only those transitions that are within the atmospheric transmission window, and 2) the existence of amplified spontaneous emission driven by pure rotational transitions.

Electron and phonon distribution relaxation in metal films under a femtosecond laser pulse

The simultaneous time evolution of electron and phonon distributions in a gold film submitted to a femtosecond laser pulse has been theoretically investigated. A system of two coupled time-dependent Boltzmann equations describing electron and phonon dynamics has been solved by considering electron–electron (e–e) and electron–phonon (e–p) collisions. Phonon–phonon (p–p) collisions have been neglected. The collision probability of each process is derived by quantum-mechanical first order perturbation theory. The injected laser energy (source term) is directly absorbed by the electron gas through electron–photon collisions and a perturbation term is added to the Boltzmann equation for electrons. However, phonons do not directly absorb energy from the laser but they are affected by the irradiation due to their collisional interaction with electrons. The results emphasize the transient non-equilibrium behavior of the electron distribution function and details of electron and phonon relaxation dynamics.

Dual laser beam modification of high alumina ceramics

Alumina-based refractory materials are extensively used in high-temperature applications, such as linings in waste incinerators. A significant problem affecting the performance of these materials is the presence of porosity and material inhomogeneity, which promote molten slag corrosion and chemical degradation. Single laser energy sources have been used in the past to densify and homogenize the surface of such ceramics. A major difficulty during laser surface treatment of brittle materials, such as ceramics, is solidification cracking due to very large temperature gradients that are developed during processing. The aim of the work presented in this article is to investigate the surface modification of 60% alumina refractory ceramics by applying two laser sources simultaneously in order to control the thermal gradients and cooling rates so that crack formation can be eliminated. The dual laser beam modified surfaces have been analyzed using optical and scanning electron microscopy, as well as electron probe microanalysis, and compared with those of single laser beam treated samples.

Characterization of High Alumina Refractory Ceramics Treated with Combined Two Laser Surface Processing

AbstractAlumina-based refractory materials are extensively used in high-temperature industrial applications, such as for linings in waste and other incinerators. The existence of porosity and material inhomogeneities can promote chemical degradation due to molten slag penetration, while impacting solid or liquid feedstock can cause erosive-wear damage. Previous research has successfully used single laser energy sources to alter the surface properties of similar ceramics, with emphasis on sealing porosity and enhancing degradation resistance. However, this process has resulted in some solidification cracking at the surface due to large temperature gradients developed during processing. In the present, ongoing work, the surface of the refractory ceramic is modified by combining two laser energy sources to control the thermal gradients and cooling rates, with the objective of eliminating crack formation. The surface morphology and microstructures of the laser-treated areas are analyzed. This paper presents some initial results from the programme.

CALYCEAL DIVERTICULA: Ureteroscopic Management

In selected cases, RIRS management of calyceal diverticula and its related problems has been shown to be more efficacious than ESWL monotherapy and avoids the potential complications and discomfort of percutaneous and laparoscopic procedures. The advent of the Holmium laser energy source, with innovations such as the flexible ureteroscope and the tipless stone basket, have expanded the role of RIRS in the management of calyceal diverticula and associated problems. Presently, RIRS is the initial treatment choice for the management of low to moderate stone burdens that are contained in calyceal diverticula or trapped behind any narrowed intrarenal segment (e.g., infundibular stenosis). If repair of the stenotic segment is not successful, thereby excluding stone treatment, then under the same anesthesia, the patient undergoes a percutaneous antegrade renal surgery. The authors feel that the percutaneous approach as a first choice is more suitable for posteriorly located diverticula with a large stone burden. In selected cases of anteriorly located diverticula with large stone burdens, the laparoscopic approach is more expedient.

Transmyocardial laser revascularization for inoperable coronary artery disease

Interest in transmyocardial laser revascularization for the treatment of otherwise inoperable coronary artery disease has increased rather dramatically in recent years. The results of several industrially sponsored clinical series have been reported recently, all with significant improvement in angina pectoris that appears both rapid and sustained. In most instances, an associated improvement in exercise tolerance has been reported. Improvement in regional myocardial perfusion has been proclaimed, although it is less consistent and less complete than symptom relief. The mechanisms whereby this clinical effect is achieved remain unknown. Histologic analysis of autopsy material has yielded somewhat conflicting results regarding the persistent patency of laser-created channels. The results of laboratory investigations of this therapy have been equally inconsistent. Despite our ignorance regarding the mechanism of angina relief, clinical experience continues to grow. In addition to the CO2 laser energy source used in early studies, trials of alternative devices using holmium:yttrium-aluminum-garnet and eximer lasers are underway. The latter two employ fiberoptic technology and are currently under development for endovascular approaches.

Endometrial ablation by hysteroscopic instillation of hot saline solution

Current methods of endometrial ablation to treat excessive uterine bleeding use laser or electrosurgical energy sources. These procedures are highly skill dependent, and numerous cases of fluid overload as well as other complications have been reported. A new method of endometrial ablation instills heated 0.9% normal saline at 80 to 90°C. The fluid is recirculated and therefore, it is possible to measure accurately and predetermine the maximum amount of allowable absorption that occurs. Animal data indicate that the procedure is effective and may be safer than current methods of endometrial ablation. Standardization of this new method will require clinical trials, initially with women undergoing hysterectomy, for proper evaluation of the extent of thermal damage in relation to the time and intensity of heat exposure.

A new laser scalpel – a brief report

One may consider the clad silica fibre cutting probe as a cheap alternative of the popular sapphire probe, sharing some of its properties. Made of silica, the scalpels have a fair heat tolerance and may be used without cooling by liquids or gas as is necessary with sapphire blades. The laser scalpel described here is driven (powered) with a 10 W cw Nd:YAG laser energy source (1064 nm) and possesses good cutting and haemostatic properties. It may also be used with lasers emitting other wavelengths. One may assume that a diode laser emitting in the near infrared (800-810 nm) may have very similar, although no analogous cutting properties when used with the described scalpel.

Heavy ion fusion research in Spain

The indirect-direct illumination scheme has been investigated, and simulations were performed using the radiation-hydrodynamics code Sara, showing good agreement with experiments performed at CEL-V Limeil (France) in the PHEBUS laser. The use of an externally guided implosion of the fuel has been suggested, where two pellets, each being accelerated from opposite mouths of a cannon barrel, will collide and implode in a central cavity. A detailed opacity model ( Jimena-Dca) has been developed that treats absorption bands that result from many-particle configurations using the original Mozskowski's formalism; our average ion model ( Jimena-Ai) also includes that model. Frequency-dependent opacities for intermediate- and high- Z plasmas have been computed and tested through the WORKOP series. An adaptive mesh scheme has been implemented in the two-dimensional Arwen code based on an implicit Riemann solver and part of a Lagrangian flux-corrected transport staggered-mesh (RMFCT) scheme. The code can handle several materials on a Eulerian mesh, and includes simple ion and laser energy sources. A two-dimensional code for radiation-hydrodynamics ( Multi-2D) has been developed that uses non-structured triangular grids, and includes arbitrary Eulerian-Lagrangian hydrodynamics, radiation transport by discrete ordinates, and laser or heavy ion beam deposition. The inventory and radiological code ACAB has been extensively used to determine the activation in inertial fusion reactors and has been improved to include pulsed regimes and fission process. A molecular dynamics code has been developed in collaboration with LLNL to study neutron damage in SiC. DENIM is actively participating as one of the main proponents of the European Heavy Ion Ignition Facility of the European authorities, together with GSI Darmstadt, ENEA Frascatti and KfK Karlsruhe.

PHYSICAL CHARACTERISTICS OF WALL AND VOLUME EMISSIONS OF X-RAY IN LASER-CAVITY TARGET

We present the studies of physical mechanisms of wall and volume emissions of X-ray for different type cavity targets on "Shen-guang" facility. The wavelength 1.053 μm, pulse shape-Gauss type, energy ～500-700J/beam, pulse width ～600-1000ps laser are used to irradiate cylindrical Hohlraum from two ends. The typical target consists of three cylindrical sections of which two ends are absorption-conver-sion regions of laser energy (source region), and the median is imploding region, which is heated by radiation energy from source region. The experiment results of X-ray wall and volume emission and some analyses are presented.