Fourth Port Research Articles

Closed-loop phase stepping in a calibrated fiber-optic fringe projector for shape measurement

Active homodyne feedback control can be used to stabilize an interferometer against unwanted phase drifts introduced by, for example, temperature gradients. The technique is commonly used in fiber-optic sensors to maintain the fiber at its most sensitive (quadrature) position. We describe an extension of the technique to introduce stabilized, pi/2-rad phase steps in a full-field interferometer. The technique was implemented in a single-mode, fiber-optic interference fringe projector used for shape measurement and can be easily applied to other fiber- or bulk-optic interferometers, for example, speckle pattern and holographic interferometers. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interfere at the fourth port of a directional coupler. The interference intensity (and hence phase) is maintained at quadrature by feedback control to a phase modulator in one of the fiber arms. Stepping between quadrature positions (separated by pi rad for light undergoing a double pass) introduces stabilized phase steps in the projected fringes (separated by pi/2 rad for a single pass). A root-mean-square phase stability of 0.61 mrad in a 50-Hz bandwidth and phase step accuracy of 1.17 mrad were measured.

Endoscopic computer-enhanced beating heart coronary artery bypass grafting

Background. Telemanipulation systems have enabled coronary revascularization on the arrested heart. The purpose of this study was to develop a technique for computer-enhanced endoscopic coronary artery bypass grafting on the beating heart. Methods. The operation was performed using the daVinci telemanipulation system. Through three ports, the left internal thoracic artery was harvested in 10 mongrel dogs (30 to 35 kg) using single right-lung ventilation and CO 2 insufflation. Through a fourth port an articulating stabilizer, manipulated from a second surgical console, was inserted to stabilize the heart. The left anterior descending artery was snared using silicone elastomer slings anchored in the stabilizer cleats and the graft to coronary artery anastomosis was performed. Results. In 7of 10 dogs, total endoscopic beating heart bypass grafting, cardiac stabilization, arteriotomy, and arterial anastomosis were performed using computer-enhanced technology. Endoscopic stabilization and temporary left anterior descending artery occlusion were well tolerated. All grafts were patent although minor strictures were found in 2. In 3 dogs, the procedure could not be completed (1 ventricular arrhythmia, 1 left atrial laceration, and 1 right ventricular outflow tract compression). Conclusions. Endoscopic beating heart coronary artery bypass grafting is possible in a canine model using a computer-enhanced instrumentation system and articulating stabilization.

Colecistectomia laparoscópica com utilização de três portos: estudo preliminar

A Colecistectomia Laparoscópica (CL) é freqüentemente realizada com quatro portos e três cirurgiões. Com o objetivo de possibilitar maior mobilidade à equipe cirúrgica e diminuir os custos do procedimento adotamos a CL por três portos. De setembro de 1994 a agosto de 1996, 169 CL por três portos foram realizadas, 133 (78,6%) no sexo feminino e 36 (21,3%) no sexo masculino. A média de idade foi de 45,6 anos. Houve a necessidade do quarto porto em três (1,8 %) e ocorreu a conversão para colecistectomia aberta em três (1,8%). Das 169 CL por três portos propostas houve sucesso em 163 (96,4%). O tempo médio do ato operatório foi de 78,4 minutos. As complicações peroperatórias ocorreram em seis casos (3,6%): lesão do ducto cístico - dois (1,2%), hemorragia do porto epigástrico - dois (1,2%), hemorragia do leito vesicular- um (0,6%), enfisema subcutâneo - um (0,6%). As complicações pós-operatórias estiveram em cinco casos (3,0%): infecção do porto umbilical - dois (1,8%), íleo prolongado - um (0,6%), coleperitôneo - um (0,6%), coledocolitíase residual- um (0,6%). Não houve óbito. Conclui-se que a CL por três portos apresenta vantagens frente à CL por quatro portos, pois propicia maior mobilidade à equipe cirúrgica, utiliza menor quantidade de instrumental laparoscópico sugerindo menor custo hospitalar e permite melhor resultado estético.

Experience with three-port laparoscopic cholecystectomy.

After considerable experience with laparoscopic cholecystectomy (LC) using four ports, we began using three-port LC in October 1993 and have performed 130 LCs with this procedure up to May 1996. The procedure was successful in 119 patients. In 6 patients fourth port was used, and in another 5, the procedure was converted to open laparo-tomy. Cooperative manipulation of the surgical instruments between the operator and assistant is very important for this procedure, for exposing Calot's triangle and dissecting the gallbladder from the gallbladder bed. The use of an ultrasonic aspiration system (Sumisonic ME 2400; Sumitomo Bakelite, Tokyo, Japan) made it easier to identify the cystic duct and artery, especially in patients with chronic inflammation or dense adhesions. We encountered no problems with cannulation into the cystic duct for intraoperative cholangiography, and there were no intra- and postoperative complications in this series. We achieved good results, similar to those achieved with the four-port technique. This technique is technically feasible and safe, and it has esthetic and cost advantages compared with the four-port technique. However, the operator who performs three-port LC should not hesitate to add another port, or to convert to open laparotomy, whenever any difficulties occur during this procedure, to prevent critical complications.

Laparoscopic Pelvic Lymphadenectomy

Eleven male patients with pelvic malignancy underwent laparoscopic lymphadenectomy for staging of their tumors. The technique allowed removal of pelvic lymph nodes in all 11 patients and metastatic disease was found in five cases, resulting in a change of recommended therapy. The technique was via a three-port exposure, although a fourth suprapubic port was occasionally used for additional retraction. A bladder laceration, which was repaired laparoscopically, was the only intraoperative complication. A pelvic hematoma was the only significant postoperative complication. Laparoscopic pelvic lymphadenectomy appears to offer a less morbid staging for those patients with a high likelihood of nodal metastasis. Laparoscopic detection of positive pelvic lymph nodes may alter the management of genitourinary malignancy and improve overall patient care.

Analysis of integrated-optics near 3 dB coupler and Mach-Zehnder interferometric modulator using four-port scattering matrix

The scattering matrix formalism for a lossless four-port device is used to describe the interferometric performance of the integrated-optics near 3 dB coupler and, consequently, the Mach-Zehnder interferometric modulator as a function of coupler and/or power imbalance. For the case of a coupler consisting of three single-mode dielectric guides forming a Y junction, a fourth port is incorporated which takes all the power radiated out of the guided-wave system in the vicinity of the junction. The interferometric properties of the coupler are shown to be relatively insensitive to fabrication and/or design errors of a magnitude which would make the use of this junction in the reverse direction as a 3 dB divider very marginal. A coupler with an extinction ratio as an interferometer better than -26 dB corresponds to a power divider which couples 22 percent more power into one arm than the other. It is also shown that the near 3 dB coupler used as the output of an interferometric modulator is similarly insensitive to the inequality of the powers in the two arms.

Analysis of Integrated-Optics Near 3 dB Coupler and Mach-Zehnder Interferometric Modulator Using Four-Port Scattering Matrix

The scattering matrix formalism for a lossless four-port device is used to describe the interferometric performance of the integrated optics near 3dB coupler and, consequently, the Mach-Zehnder interferometric modulator as a function of coupler and/or power imbalance. For the case of a coupler consisting of three single-mode dielectric guides forming a Y junction, a fourth port is incorporated which takes W the power radiated out of the guided-wave system in the vicinity of the junction. The interferometric properties of the coupler are shown to be relatively insensitive to fabrication and/or design errors of a magnitude which would make the use of this junction in the reverse direction as a 3 dB divider very marginal. A coupler with an extinction ratio as an interferometer better than -26 dB corresponds to a power divider which couples 22 percent more power into one arm than the other. It is also shown that the near 3 dB coupler used as the output of an interferometric modulator is similarly insensitive to the inequality of the powers in the two arms.

Singapore: Its Growth as an Entrepot Port, 1819–1941

Once the premier port in colonial Southeast Asia and one of the foremost in the British Empire, Singapore now ranks as the world's fourth busiest port, tonnagewise, with the second highest per capita G.D.P. in Asia. Its post-war achievements rest on solid historical advantages. A broad historical survey of its commercial growth before World War II is therefore not amiss: the more so, as there has been no such panoramic presentation before. With no natural resources, Singapore's economic growth was almost synonymous with its foreign trade. In most historical works, especially those written before World War II, Singapore has been treated as an integral part of the Straits Settlements or British Malaya, for, until its emergence as a separate nation in August 1965, Singapore as the focal point of reference for researches was not part of the historical consciousness.

SEATTLE, THE FOURTH PORT OF THE UNITED STATES

School Science and MathematicsVolume 18, Issue 5 p. 459-459 SEATTLE, THE FOURTH PORT OF THE UNITED STATES First published: May 1918 https://doi.org/10.1111/j.1949-8594.1918.tb03833.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue5May 1918Pages 459-459 RelatedInformation