Interfacing Branching Random Walks with Metropolis Sampling: Constraint Release in Auxiliary-Field Quantum Monte Carlo.

We present an approach to interface branching random walks with Markov chain Monte Carlo sampling and to switch seamlessly between the two. The approach is discussed in the context of auxiliary-field quantum Monte Carlo (AFQMC) but can be applied to other Monte Carlo calculations or simulations. In AFQMC, the formulation of branching random walks along imaginary-time is needed to realize a constraint to control the sign or phase problem. The constraint is derived from an exact gauge condition and is in practice implemented approximately with a trial wave function or trial density matrix, which can break exactness in the algorithm. We use the generalized Metropolis algorithm to sample a selected portion of the imaginary-time path after it has been produced by the branching random walk. This interfacing allows a constraint release to follow seamlessly from constrained-path sampling, which can reduce the systematic error from the latter. It also provides a way to improve the computation of correlation functions and observables that do not commute with the Hamiltonian. We illustrate the method in atoms and molecules, where improvements in accuracy can be clearly quantified and near-exact results are obtained. We also discuss the computation of the variance of the Hamiltonian and propose a convenient way to evaluate it stochastically without changing the scaling of AFQMC.

Long-term results of the paraesophagogastric devascularization with or without esophageal transection: which is more suitable for variceal bleeding?

BACKGROUND: It has been reported that the paraesophagogastric devascularization with esophageal transection procedure, also known as the modified Sugiura procedure, was effective in the treatment of variceal bleeding. However, it was not widely accepted by other surgeons because of the high rate of rebleeding, complications, and mortality. To discover the effects of the paraesophagogastric devascularization procedure and the modified Sugiura procedure, we retrospectively analyzed the outcomes of these two procedures. MATERIALS AND METHODS: During January 1990 and December 2009, 278 patients with variceal bleeding underwent devascularization after failed pharmacotherapy and endotherapy. In these 278 patients, 180 underwent paraesophagogastric devascularization without esophageal transection (group I), and the other 98 patients were subjected to the modified Sugiura procedure (group II). RESULTS: Postoperative mortality was 7.2% in group I, and 9.2% in group II (P = 0.563). The postoperative rebleeding rate in the two groups was 2.2 and 3.1%, respectively (P = 0.474). After a mean follow-up of 67.9 ± 37.3 months and 67.4 ± 44.6 months, respectively, esophageal transaction-related morbidity (leak, bleeding, and stricture) was 8.2% (8/98) in group II and 0% (0/180) in group I (P < 0.001). The overall rebleeding rate was 27% (41/152) in group I, and 27.2% (22/81) in group II (P = 0.976). The overall mortality was 28.3% (43/152) in group I, and 28.4% (23/81) in group II (P = 0.986). CONCLUSIONS: In the management of variceal bleeding, paraesophagogastric devascularization without esophageal transection is as effective and safe as devascularization with esophageal transaction, but with less esophageal transection-related morbidity.

Comparison of duct-to-mucosa and end-to-side pancreaticojejunostomy reconstruction following pancreaticoduodenectomy.

BACKGROUND/AIMS: Pancreaticojejunostomy reconstruction following pancreaticoduodenectomy still remains a debate because of high incidence of complications. To compare the effect of duct-to-mucosa and end-to-side pancreaticojejunostomy reconstruction following pancreaticoduodenectomy, we retrospectively reviewed two groups of patients who underwent duct-to-mucosa or end-to-side pancreaticojejunostomy reconstruction. METHODOLOGY: Over a period of 6 years, 240 consecutive patients underwent duct-to-mucosa (group A) or end-to-side (group B) pancreaticojejunostomy reconstruction following pancreaticoduodenectomy. RESULTS: There were no statistical differences between group A and B in regards to age, gender, preoperative serum levels of total bilirubin, alanine aminotransferase, albumin, pathological features, amount of intraoperative bleeding and duration of operation. The overall incidence of postoperative complications was 26.7 % (22.2% in group A, 30.3% in group B, p>0.05). Of 108 patients in group A, pancreatic fistula occurred in 10 (9.3%) patients and of 132 patients in group B, pancreatic fistula occurred in 14 (10.6%) patients (p>0.05). The overall hospital mortality was 4.2% (3.7% in group A, n=4; 4.5% in group B, n=6, p>0.05). The postoperative hospital stay (mean ±SD) for group A was 20.3±19.7 days, for group B was 23.3+14.3 days (p>0.05). CONCLUSIONS: Our results showed no statistical difference between the two techniques in decreasing postoperative complications including pancreatic fistula or postoperative hospital stay.

Duodenal pseudolymphoma: a case report and review of literature.

We report a rare case of duodenal pseudolymphoma without any symptoms. The lesion located in front of the head of the pancreas was found accidentally during a medical examination. The findings of computed tomography and positron emission tomography-computed tomography suggested a stromal tumor or malignant lymphoma. Surgical resection was performed. The lesions were pathologically diagnosed as duodenal pseudolymphoma.

Silencing Fas-associated phosphatase 1 expression enhances efficiency of chemotherapy for colon carcinoma with oxaliplatin.

AIM: To investigate whether silencing Fas-associated phosphatase 1 (FAP-1) expression enhances the efficiency of chemotherapy for colon carcinoma with oxaliplatin. METHODS: Expression of FAP-1 in mRNA and protein was detected by reverse transcription polymerase chain reaction (RT-PCR) and flow cytometry. Small interfering RNA (siRNA) was designed according to the FAP-1 mRNA sequence. Cell proliferation was evaluated by methyl thiazolyl tetrazolium (MTT) assay. Anenxin V- and propidine iodine (PI) were assayed by flow cytometry for the detection of apoptosis. RESULTS: The expression of FAP-1 was increased in SW480 cells after chemotherapy with oxaliplatin. Transfection of FAP-1 siRNA into SW480 cells silenced the expression of FAP-1 and consequently abolished the inhibitory function of Fas/FasL-mediated apoptosis pathway, thus increasing the efficacy of chemotherapy for colon carcinoma with oxaliplatin. CONCLUSION: RNA interference combined with conventional chemotherapy is more effective against colon cancer.