No abstract

PurposeDownstaging after chemoradiotherapy (CRT) for rectal cancer usually occurs. The present study aimed to evaluate pathologic y-stage (yp-stage) and its influence on local recurrence and systemic recurrence in rectal cancer patients treated with CRT followed by surgical resection.MethodsWe retrospectively analyzed 261 patients underwent preoperative CRT and radical resection for rectal cancer between August 2004 and December 2010. Patients received preoperative CRT consisting of 5-fluorouracil and leucovorin delivered with concurrent pelvic radiation of 45.0-50.4 Gy, followed by radical surgery at 6-8 weeks after CRT.ResultsOf the 261 patients, 24 (9.2%) had yp-stage 0, 83 (31.8%) had yp-stage I, 86 (32.9%) had yp-stage II, and 68 (26.1%) had yp-stage III. Patients with yp-stage III had a greater prevalence of preoperative CEA, poorly differentiated tumor, lymphovascular invasion (LVI) and perineural invasion (PNI) than patients with lower yp-stages. We found that yp-stage, preoperative CEA, LVI, PNI and tumor regression grade were significant prognostic factors for both local and systemic recurrence. In multivariate analysis, yp-stage, LVI and PNI were significant factors for local and systemic recurrence. During the median follow-up of 37.5 months, the five-year local recurrence-free survival rate was 100.0%, 95.0%, 89.3%, and 80.6% of yp-stage 0-III, respectively. The five-year systemic recurrence-free survival was 95.8%, 75.3%, 71.4%, and 48.8% of yp-stages 0-III, respectively.ConclusionThe yp-stage after preoperative CRT for rectal cancer is closely correlated with local and systemic recurrence-free survival. Therefore, yp-stage should be considered as a prognostic factor for rectal cancer patients having a course of preoperative CRT.

Prediction of the ROHR (rate of heat release) and NOx production in medium-speed marine diesel engines was investigated. The subject of this paper is qualitative and quantitative evaluation of the numerical results. FIRE code v8.1 was used to examine the behavior of spray and combustion phenomena in diesel engine. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation. The spray visualization was performed experimentally in the constant-volume high-pressure chamber to clarify numerical results on the spray characteristics of the spray angle and penetration. Time-resolved spray behaviors were captured by high-speed digital camera. The simulation results were tested with the experimental data of the real engine. Finally, with adjustment of some model constants, reasonable agreements between experimental and simulated results on the ROHR and NOx were shown.

Numerical simulations and experiments have been carried out to meet the next IMO(International Maritime Organization) Tier2 NOx regulations, which would be determined to reduce about 19-2 1% ofthe current limit for medium-speed diesel engine. The selected paraineters in this study are piston bowl shape, fuel iajection nozzle configuration and fuel iniection rate. The behavior of spray and combustion phenomena in diesel engine was examined by the three-dimensional FIRE code. As a droplet breakup model, the wave breakup model was used. In order to predict spray characteristics accurately in the wide range ofambient gas densitM the model constant Bi with respect to breakup time was set as a functien of ambient gas density p, Bi=1.4239xp+O.2093. The spray visualization experiment was perforrned in the constant-volume high-pressure chamber to clarify the numerieal results on the spray characteristics of the spray angle and penetration. The fuel iajection rig test was perfbrmed to know the fuel irijection rate prQfile as an input data fbr the numerical analysis by using Bosch-tube irijection rate metes, The computational results fbr the two different nozzle configurations were verified with the experimental data on the cytinder pressure, fuel consumption and NOx formation through adjustment of some model constants at 50% load, The effects of fuel iojection nozzle, piston bowl and fuel iajection rate on the engine perfbrmance were investigated to find the optimum parameters on NOx control. Finally, 23.7% NOx reduction could be achieved with O,71% deterioration in fuel consumption to meet the next IMO Tier2 regulations.