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Over the past decade, there have been many advances in the management of bleeding in children undergoing heart surgery. These advances have included changes in surgery, anesthesiology, and cardiopulmonary bypass (CPB). Surgeons routinely use hemostatic agents instilled directly at the site of bleeding in the form of gels and sponges (1). Anesthesiologists are using newer drugs such as factor VIIa (2) and older drugs such as aminocaproic acid, which have resurfaced after the recall of aprotinin (1). Anesthesiologists are monitoring the clotting process with thromboelastography, which is more dynamic than traditional clotting tests such as prothrombin time (3). Cardiopulmonary bypass circuits have become smaller and more biocompatible leading to decreased contact activation of the inflammatory response and potentially mitigating CPB’s effects on hemostasis. Perfusionists routinely use various forms of ultrafiltration in an attempt to hemoconcentrate red blood cells and clotting factors during (conventional ultrafiltration) and immediately after (modified ultrafiltration [MUF]) CPB. We recently introduced a change in our blood product transfusion practice in an attempt to decrease volume shifts during the MUF process and promote earlier hemostasis. Instead of administering all of the blood products intravenously after CPB and MUF, we changed to administering blood products during MUF, directly into the MUF circuit. This article describes a retrospective study of this change in practice.

A new optical system for controlling spatial profile of laser beam has been developed. The principle of the system controls independently transverse and longitudinal diameters of the laser beam. The system consists of cylindrical mirrors and integration mirrors which focus the beam in directions perpendicularly intersecting with each other. In order to investigate the focusing property of the optical system, a calculating model for predicting beam paths through the optical system has beendeveloped using the ray tracing method. According to the model, three typical optical systems for a line shape focused beam have been designed-(1), two cylindrical mirrors, (2) one cylindrical mirror and one integration mirror, and (3) one cylindrical mirror and one integration mirror with convex segments. After laser heating experiments of steel by using these optical systems, it has been proved that they are useful in actual industrial applications.

In spite of recent rapid progress of high power solid state laser, CO2 laser systems are still useful for metal drilling with hole diameter of about 100 µm and depth of several tens of µm, because it requires large pulse energy of about 100 mJ with high beam quality. Mechanically Q-switched CO2 laser systems are favorable for such application with high repetition rate (>10 kHz) [1,2] and have the advantage of cost performance.In spite of recent rapid progress of high power solid state laser, CO2 laser systems are still useful for metal drilling with hole diameter of about 100 µm and depth of several tens of µm, because it requires large pulse energy of about 100 mJ with high beam quality. Mechanically Q-switched CO2 laser systems are favorable for such application with high repetition rate (>10 kHz) [1,2] and have the advantage of cost performance.

High-speed etching of polyimide films used as insulators for multi-layered printed circuit boards has been investigated usinga 0-switched CO2 laser tuned at 9.3 im. A mechanical chopper inserted in the cavity realizes the 0-switching operation. Thepulse repetition rate of the laser is as high as several tens of kHz, so that continuous processing of certain width is possiblewithout beam aiming to each hole. The laser beam is scanned by a galvano-mirror and then focused to the work by a telecentriclens. Metal layer on the top of the printed-circuit board is used as a contact mask, and it works as a multi-reflector inconjunction with a reflector placed above. Multi-reflection increases the processing speed by a factor of 2.5. Overall process-ing speed is 1.5 rn/mm for 0.1 m width or 0.15 m2/min. Keywords: polyimide, polymer, printed-circuit, etching, laser, 0-switch, CO2 laser 1. INTRODUCTION With the recent progress of electric tools such as mobile telephones, digital cameras, and personal computers especially intheir sizes, device-mounting density for the PCBs (print-circuit boards) are rapidly rising. Such situation has derived themulti-layered PCB technology. For these multi-layered PCBs, etching of insulator such as polyimide between metal layers isnecessary for inter-layer connection. A hole that connects layers is called as a blind hole. Interest in laser etching of polyimideresides in its ability of precise high speed processing. Most of organic polymers show the strong absorption in IR (infrared)region as well as in UV (ultraviolet) region. Thus most of laser-etching machines employ excimer lasers or TEA (transverselyexcited atmospheric-pressure) CO2 lasers as beam sources because their high peak powers are suitable for drilling1'2. Nowa-days TEA CO2 laser based systems are growing up in the market of laser-etching machines mainly due to their low running-cost and free of life-hazard gases in contrast to excimer laser based systems. However, since the pulse repetition frequency of

The polymers ablation by a Q-switched C02 laser is demonstrated and compared with that of the conventionalTEA laser ablation. The 20 - 100 m depth ablative etching of PET with well defined edge were successfully obtainedwhen the strong absorbed 9R(20) line at 1078.57cm1was irradiated. It was found the ablation characteristics by a Q-switched laser was almost same as that by a TEA laser.Keywords: Q-switched C02 laser, Ablation, Organic polymers, Laser materials processing 1. INTRODUCTION Since early works of laser ablation using excimer laser 2, lot of studies focused on its mechanism have beenreported. Many applications such as micro-machining of polymers, surface cleaning of solid and superconducting thin-filmdeposition are expected by using a laser ablation. Most of organic polymers show the strong absorption in IR region aswell as in UV region, the pulsed C02 laser can also ablate these materials successfully. In order to avoid the thermaldamage, a short duration and high peak power pulse is preferable for laser ablation. Therefore, TEA C02 laser was adoptedfor the IR laser ablation studies35. Werner and Schweizer reported the paint stripping of aircraft using commerciallyavailable TEA C02 laser of 2kW average power3. Brannon and Lankard studied the ablative etching of Polyimide, which isthe insulating material for micro-electronic device, using a tunable TEA C02 laser. They pointed out that Polyimide can beetched clearly and precisely by selecting the proper C02 laser line at strong absorption band4.For the industrial applications of the laser ablations, it requires a high average power (pulse repetition frequency

Performance characteristics of a high power Q-switched CO2 laser based on a fast gas flow system have been investigated. A combination of a fast rotating chopper and an intracavity telescope as a Q-switching device has been applied to a fast axial flow, dc- discharged 1.5 kW continuous wave CO2 laser. The laser delivered 480 W average output power at 12 kHz pulse repetition rate on a free-running basis. Peak power of each Q-switched pulse is approximately 100 kW, and the pulse duration is 250 nsec. An analytical model describing the unique characteristics of the CO2 laser medium and of the rotating chopper Q-switching technique has been developed and applied to the experimental results. Good agreement was obtained between the theory and experiment for various pulse parameters such as peak power, pulse duration, and pulse buildup time. A method to improve the pulse characteristics using a fast axial gas flow system is proposed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A compact high-power Q-switched CO2 laser has been developed using a combination of intense pulsed rf (13.56 MHz) discharge excitation and a high-speed rotating Q-switch chopper. Performance characteristics have been investigated as functions of Q-switching velocity, input discharge energy density and laser gas composition. A pulse peak power of 300 kW and an average power of 740 W at 10 kHz pulse repetition frequency have been obtained simultaneously for a Q-switched laser based on a CO2 laser with 1.1 kW average power. By decreasing the repetition frequency to 4 kHz, the peak power was enhanced to above 500 kW. An analytical model describing the unique features of the Q-switched CO2 laser has also been developed for quantitative evaluation of the laser performance. Good agreement was obtained between the theoretical model and experimental results.