RESUMEN

Optimization of user-defined parameters (Dmax, Nmin, order (K)) in the Density-based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, used to characterize nanoclusters in Al-0.9% Mg-1.0% Si-0.3% Cu (mass %), was conducted. Ten combinations of parameters with a given K were considered for samples naturally aged (NA) and preaged (PA) at 100°C. We confirmed four types of unphysical clusters, artificially formed, by analyzing composition with size, atomic density, and atomic arrangement inside clusters. The optimum combinations minimizing those unphysical clusters were obtained for both NA and PA samples. Meanwhile, to evaluate the reliability of the optimum combination, volume rendering and isosurfacing were performed. As a result, regions of high solute concentration were confirmed, and those regions are in good agreement with the position of the clusters obtained by applying the optimum combination in DBSCAN. Furthermore, by comparing the optimum combinations with the fixed parameters widely used until now, we showed that for each dataset, considering independent parameters obtained in the same method is desirable rather than using fixed parameters. Consequently, an idea of determining the algorithm parameters for characterizing the nanoclusters in Al-Mg-Si(-Cu) alloys was introduced.

RESUMEN

As the environmental pollution issue has recently become significant, environmental regulations in Europe and the United States are being strengthened. Thus, there is a demand for the quality improvement of emission after-treatment systems to satisfy the strengthened environmental regulations. Reducing the amount of welding heat distortion by optimization of the welding order of each part could be a solution for quality improvement since the emission after-treatment system consists of many parts and each assembly is produced by welding individual ones. In this research, a method to derive a welding sequence that effectively minimizes welding deformation was proposed. A two-stage simulation was performed to obtain the optimal welding sequence. In the first stage, the welding sequence was derived by analyzing the number of welding groups in each assembly of a structure. The derived welding sequence was verified by performing a thermal elasto-plastic analysis and comparing it with the experimental results.

RESUMEN

PURPOSE: Proctectomy for the treatment of rectal cancer results in inevitable changes to bowel habits. Symptoms such as fecal incontinence, constipation, and tenesmus are collectively referred to as low anterior resection syndrome (LARS). Among the several risk factors that cause LARS, anastomotic leakage (AL) is a strong risk factor for permanent stoma formation. Therefore, the purpose of this study was to investigate the relationship between the severity of LARS and AL in patients with rectal cancer based on the LARS score and the Memorial Sloan Kettering Cancer Center (MSKCC) defecation symptom questionnaires. METHODS: We retrospectively analyzed patients who underwent low anterior resection for rectal cancer since January 2010. Patients who completed the questionnaire were classified into the AL group and control group based on medical and imaging records. Major LARS and MSKCC scores were analyzed as primary endpoints. RESULTS: Among the 179 patients included in this study, 37 were classified into the AL group. After propensity score matching, there were significant differences in the ratio of major LARS and MSKCC scores of the control group and AL group (ratio of major LARS: 11.1% and 37.8%, P<0.001; MSKCC score: 67.29±10.4 and 56.49±7.2, respectively, P<0.001). Univariate and multivariate analyses revealed that AL was an independent factor for major LARS occurrence and MSKCC score. CONCLUSION: This study showed that AL was a significant factor in the occurrence of major LARS and defecation symptoms after proctectomy.

RESUMEN

Purpose: Drain insertion after proctectomy is common in clinical practice, although the effectiveness of drains has been questioned. However, drains are commonly displaced after surgery. We hypothesized that drain displacement is associated with clinical outcomes and aimed to assess differences in clinical outcomes, such as overall morbidity, including anastomotic leakage (AL), reintervention rates, length of hospital stay, and mortality rates, between patients who experienced displaced drains and those who did not. Methods: Rectal cancer patients who underwent proctectomy at a single institution between January 2015 and December 2020 were retrospectively reviewed. Clinical characteristics were compared between patients who experienced displaced drains and those who did not. The primary endpoint was the occurrence of reintervention in patients with AL. The secondary endpoints were overall morbidity rates, AL rates, length of hospital stay, and mortality within 30 days. Results: Among 248 patients who underwent proctectomy, 93 (37.5%) experienced displaced drains. A higher proportion of patients who experienced displaced drains required reintervention due to AL than those who did not experience displaced drains (odds ratio, 3.61; 95% confidential interval, 1.20-10.93; p = 0.016). However, no significant difference was found in the overall morbidity rate, mortality, and length of hospital stay between the groups. Conclusion: Drain displacement does not worsen outcomes such as overall morbidity rate, mortality, and length of hospital stay after proctectomy but is associated with an increase in the need for reintervention in patients with AL.

RESUMEN

Two types of nanoclusters were detected using DSC thermal analysis operating at -50 °C with liquid nitrogen. The formation of Cluster (1) was substantially suppressed by the formation of Cluster (2) during step quenching at 100 °C for 0.06 ks. The hardness increase was retarded for a period during two-step aging at 170 °C in the case of natural aging for 604.8 ks. The hardness decrease was determined to be due to the dissolution of nanoclusters in the early stage of two-step aging at 170 °C. On the other hand, hardness was directly increased in the step-quenched samples during multi-step aging at 170 °C. It is noted that Cluster (2) directly transforms into the strengthening phase. The bake hardening response is fairly enhanced by the formation of Cluster (2), which is formed by the step quenching process. It was confirmed that the step-quenched samples had a higher number of precipitates than the naturally-aged ones based on TEM images. The structure of the precipitate was identified to be the ß″ phase by analyzing HRTEM image.

RESUMEN

Purpose: Hand-eye discordance during laparoscopic colon surgery is an obstacle to the assistant. We evaluated the usefulness of a 180° rotatable laparoscopic monitor for the colorectal surgery assistant to overcome hand-eye discordance. Methods: Twenty-six residents of the department of surgery (novice group, n=13; experienced group, n=13) participated in this study. They performed grasping a ring and transferring it to standing bars on a laparoscopic training kit under the conventional view and a 180° rotated monitor view. We defined successful performance when this procedure was completed in 3 minutes. Results: The number of successful performance was higher under the 180° rotated monitor view than under the conventional view monitor (6.88±2.79 vs. 0.92±0.80, p<0.01). Under the 180° rotated monitor view, the experienced group had a higher number of successful performances than the novice group (8.31±2.59 vs. 5.46±2.26, p=0.009). However, no statistically significant difference was found between the two groups under the conventional view (1.23±0.93 vs. 0.62±0.51, p=0.091). Conclusion: This study shows the usefulness of a 180° rotated monitor view to overcome hand-eye discordance, which adversely affects the laparoscopic performance of the colorectal surgery assistant.

RESUMEN

Fe is intentionally added in order to form the Fe intermetallic compounds (Fe-IMCs) during casting. Field emission scanning electron microscope with energy dispersive spectrometer (EDS) was conducted to understand microstructural changes and chemical composition analyses. The needlelike Fe-IMCs based on two dimensional observation with hundreds of micro size are modified to fragmented particles with the minimum size of 300 nm through clod rolling with 80% thickness reduction. The ratio of Fe:Si on the fragmented Fe-IMCs after 80% reduction is close to 1:1, representing the ß-Al5FeSi. The yield and tensile strengths are increased with increasing reduction rate. On the other hand, the elongation is decreased with the 40% reduction, but slightly increased with the 60% reduction. The elongation is dramatically increased over two times for the specimen of 80% reduction compared with that of the as-cast. Fracture behavior is strongly affected by the morphology and size of Fe-IMCs. The fracture mode is changed from brittle to ductile with the microstructure modification of Fe-IMCs.

RESUMEN

Influence of Mg contents with the natural aging (NA) time on the two-step aging behavior in Al-Mg-Si alloys is studied. Hardness is gradually increased during NA in the 3M4S, whereas dramatic increase of hardness after NA for 3.6 ks is confirmed in the 9M4S. Similar peak hardness is confirmed between the two-step aged and single aged samples in the 3M4S. It means that there is no negative effect of two-step aging. On the other hand, the peak hardness is decreased for the naturally-aged sample compared with the single aged one in the 9M4S. Formation of Cluster (1) is accelerated by the Mg addition, resulting in the negative effect of two-step aging. Meanwhile, the formation of the precipitates is accelerated by Mg addition during aging at 170 °C. The precipitate formed at the peak hardness during aging at 170 °C after natural aging for 43.2 ks is identified as the ß″ phase based on the high resolution transmission electron microscope observation.

RESUMEN

The age-hardening is enhanced with the high cooling rate since more vacancies are formed during quenching, whereas the stable beta phase is formed with the slow cooling rate just after solid solution treatment resulting in lower increase of hardness during aging. Meanwhile, the nanoclusters are formed during natural aging in Al-Mg-Si alloys. The formation of nanoclusters is enhanced with increasing the Si amount. High quench sensitivity based on mechanical property changes was confirmed with increasing the Si amount. Moreover, the nano-size beta" phase, main hardening phase, is more formed by the Si addition resulting in enhancement of the age-hardening. The quench sensitivity and the formation behavior of precipitates are discussed based on the age-hardening phenomena.

RESUMEN

BACKGROUND: Approximately 20 % of all patients with colorectal cancer are diagnosed as having Stage IV cancer; 80 % of these present with unresectable metastatic lesions. It is controversial whether chemotherapy with or without primary tumor resection (PTR) is effective for the treatment of patients with colorectal cancer with unresectable metastasis. Primary tumor resection could prevent tumor-related complications such as intestinal obstruction, perforation, bleeding, or fistula. Moreover, it may be associated with an increase in overall survival. However, surgery delays the use of systemic chemotherapy and affects the systemic spread of malignancy. METHODS/DESIGN: Patients with colon and upper rectal cancer patients with asymptomatic, synchronous, unresectable metastasis will be included after screening. They will be randomized and assigned to receive chemotherapy with or without PTR. The primary endpoint measure is 2-year overall survival rate and the secondary endpoint measures are primary tumor-related complications, quality of life, surgery-related morbidity and mortality, interventions with curative intent, chemotherapy-related toxicity, and total cost until death or study closing day. The authors hypothesize that the group receiving PTR following chemotherapy would show a 10 % improvement in 2-year overall survival, compared with the group receiving chemotherapy alone. The accrual period is 3 years and the follow-up period is 2 years. Based on the inequality design, a two-sided log-rank test with α-error of 0.05 and a power of 80 % was conducted. Allowing for a drop-out rate of 10 %, 480 patients (240 per group) will need to be recruited. Patients will be followed up at every 3 months for 3 years and then every 6 months for 2 years after the last patient has been randomized. DISCUSSION: This randomized controlled trial aims to investigate whether PTR with chemotherapy shows better overall survival than chemotherapy alone for patients with asymptomatic, synchronous unresectable metastasis. This trial is expected to provide evidence so support clear treatment guidelines for patients with colorectal cancer with asymptomatic, synchronous unresectable metastasis. TRIAL REGISTRATION: Clinicaltrials.gov NCT01978249 .

Asunto(s)

RESUMEN

BACKGROUND: Ileostomy closure is a minor procedure and is performed through a small peristomal incision. However, a hard adhesion increases the technical difficulty. A peritoneofascial suture (PFS) will reduce the adhesion layers of the abdominal wall. This study was performed to evaluate whether the PFS method may decrease the extent of adhesions between the bowel and the abdominal wall opening and facilitate ileostomy mobilization. METHODS: Forty-two patients (24 males and 18 females) with a mean age of 57 years (range = 31-80 years) and who were undergoing ileostomy closure were enrolled. The PFS group and the conventional group had 18 and 24 patients, respectively. The intraoperative findings such as degree of adhesion, mobilization time, and associated bowel injury were analyzed. RESULTS: The thickness of the abdominal wall and the rectus abdominis was similar in both groups. The overall operation time was shorter in the PFS group than in the conventional group (50.9 vs. 80.4 min, respectively, p = 0.001). The ileostomy mobilization time was also shorter in the PFS group than in the conventional group (18.9 vs. 44.7 min, respectively, p < 0.001). The procedure was technically easier in the PFS group more frequently than in the conventional group (77.8 % vs. 31.6 %, respectively, p = 0.013). Bowel injury during mobilization was more common in the conventional group than in the PFS group (50.0 % vs. 16.7 %, respectively, p = 0.053). CONCLUSIONS: The peritoneofascial suture method is a simple procedure, and it may facilitate ileostomy mobilization by decreasing adhesion layers. To confirm the technical advantage of this method a randomized study will be needed.

Asunto(s)

RESUMEN

Inflammatory pseudotumor is a rare benign lesion mimicking malignancy both clinically and radiologically. An accurate diagnosis is still difficult and is based on the histological examination. Since inflammatory pseudotumor is exceptionally rare in the colon, this unexpected lesion can be mistaken for malignancy. We report the first case of inflammatory pseudotumor in the colon that showed (18)F-fluorodeoxyglucose (FDG) uptake and acted as the lead point causing colocolic intussusception.

Asunto(s)

RESUMEN

PURPOSE: Urinary retention in common benign anal surgery is a burden to ambulatory surgery. A pudendal nerve block was used in hemorrhoid surgery to reduce voiding complications. METHODS: The effects of a pudendal nerve block in anal surgery were compared with those of spinal anesthesia. In this prospective study, 163 consecutive patients who underwent elective hemorrhoids surgery by a single surgeon were randomized to receive pudendal nerve block (pudendal group) with 0.5 percent bupivacaine (n = 81) with 1:20,000 epinephrine or spinal anesthesia (spinal group) with 0.5 percentbupivacaine (n = 82). RESULTS: There were no statistically significant differences in the patient demographics, total amount of fluid administered, time to the onset of anesthesia, or intraoperative pain. All patients had a successful block during surgery. However, puborectalis muscle relaxation was not complete in the pudendal group. The time from the injection of the anesthetics to the first sensation of pain was longer in the pudendal group (9.1 vs. 3.1 hours; P < 0.001). Urinary catheterization was required in only 6 patients in the pudendal group compared with 57 patients in the spinal group (P < 0.001). The degree of pain was significantly lower in the pudendal group (2.7 vs. 5.2, Visual Analog Scale; P < 0.001). The amount of analgesics injected was significantly lower in the pudendal group (16/81 vs. 45/82; P < 0.001). CONCLUSIONS: A pudendal nerve block with bupivacaine results in fewer postoperative voiding complications and less pain compared with the traditional spinal anesthesia in a hemorrhoidectomy.

Asunto(s)