A robust scheme for free surface and pressurized flows in channels with arbitrary cross-sections

Flows in closed channels, such as rain storm sewers, often contain transitions from free surface flows to pressurized flows, or viceversa. These phenomena usually require two different sets of equations to model the two different flow regimes. Actually, a few specifications for the geometry of the channel and for the discretization choices can be sufficient to model closed channel flows using only the open channel flow equations. Transitions can also occur in open channels, like those from super- to subcritical flow, or vice versa. These particular flows are usually difficult to reproduce numerically and strong restrictions are imposed on the numerical scheme to simulate them. In this paper, an implicit finite-difference conservative algorithm is proposed to deal properly with these problems. In addition, a special flux limiter is described and implemented to allow accurate flow simulations near hydraulic structures such as weirs. A few computational examples are given to illustrate the properties of the scheme and the numerical solutions are compared with experimental data, when possible

A high resolution scheme for flows in open channels with arbitrary cross-section

The aim of this paper is to present a numerical scheme to simulate unsteady, one dimensional flows in open channels with arbitrary cross-section. This scheme is fully conservative of volume and momentum and preserves the non-negativity of the water depth. The finite difference method derived is semi-implicit in time and based on a space staggered grid. A high resolution technique, the flux limiter method, is implemented to control the accuracy of the proposed scheme. Our purpose is to achieve the precision and the stability of the method with respect to the regularity of the data. A few computational examples on classical test cases are given to illustrate the properties of the present method in terms of stability, accuracy and efficiency

Estimate of seismic surface energy from microstructural studies of pseudotachylyte-bearing faults

openThe total energy budget of an earthquake is one of the great unknowns in geology. From geological, seismological and laboratory evidences it is clear that the total energy of a seismic event is converted into seismic waves together with dissipation processes such as heat, fracture and friction. One of the sinks of seismic energy is the fracture energy required to propagate the fault surface and produce the surrounding damage zone. This thesis aims at estimating this parameter through the analysis of microfracture patterns found in the wall rock of a pseudotachylyte-bearing fault of the Gole Larghe Fault Zone (Adamello massif, Italy). Knowing the magnitude of the surface fracture energy it will be possible to make some considerations on the total energy of a seismic event. Understanding its partitioning is fundamental to also understand the mechanics of earthquakes.The total energy budget of an earthquake is one of the great unknowns in geology. From geological, seismological and laboratory evidences it is clear that the total energy of a seismic event is converted into seismic waves together with dissipation processes such as heat, fracture and friction. One of the sinks of seismic energy is the fracture energy required to propagate the fault surface and produce the surrounding damage zone. This thesis aims at estimating this parameter through the analysis of microfracture patterns found in the wall rock of a pseudotachylyte-bearing fault of the Gole Larghe Fault Zone (Adamello massif, Italy). Knowing the magnitude of the surface fracture energy it will be possible to make some considerations on the total energy of a seismic event. Understanding its partitioning is fundamental to also understand the mechanics of earthquakes

Effect of donor age and sex on the outcome of liver transplantation

We correlated donor and recipient factors with graft outcome in 436 adult patients who underwent 462 liver transplants. Donor variables analyzed were age, gender, ABO blood group, cause of death, length of stay in the intensive care unit, use of pressors or pitressin, need for cardiopulmonary resuscitation, terminal serum transaminases, and ischemia time. Recipient variables analyzed were age, gender, primary diagnosis, history of previous liver transplant, ABO blood group, cytotoxic antibody crossmatch, United Network for Organ Sharing (UNOS) status, and waiting time (except for the cross-match results, they were all known at the time of the operation). The endpoint of the analysis was graft failure, defined as patient death or retransplantation. Using multivariate analysis, graft failure was significantly associated with donor age, donor gender, previous liver transplantation, and UNOS 4 status of the recipient. The effect of donor age became evident only when they were older than 45 years. Livers from female donors yielded significantly poorer results, with 2-year graft survival of female to male 55% (95% CI, 45% to 67%); female to female, 64% (95% CI, 54% to 77%); male to male, 72% (95% CI, 66% to 78%); and male to female, 78% (95% CI, 70% to 88%). The only donors identified as questionable for liver procurement were old (-60 years) women in whom the adverse age and gender factors were at least additive. However, rather than discard even these livers, in the face of an organ shortage crisis, their individualized use is suggested with case reporting in a special category. © 1995

Surgical Approach for Long-term Survival of Patients With Intrahepatic Cholangiocarcinoma: A Multi-institutional Analysis of 434 Patients.

OBJECTIVES To examine the outcomes of a hepatectomy for intrahepatic cholangiocarcinoma (IHC) and to clarify the prognostic impact of a lymphadenectomy and the surgical margin. Large series of patients who were surgically treated for IHC are scarce. Thus, prognostic factors and long-term survival after resection of IHC remain uncertain. DESIGN Prospective study of patients who were surgically treated for IHC. Clinicopathologic, operative, and long-term survival data were analyzed. SETTING Prospectively collected data of all consecutive patients with pathologically confirmed IHC who had undergone liver resection with a curative intent at 1 of 16 tertiary referral centers were entered into a multi-institutional registry. PATIENTS All consecutive patients who underwent a hepatectomy with a curative intent for IHC (1990-2008) were identified from a multi-institutional registry. RESULTS A total of 434 patients were included in the analysis. Most patients underwent a major or extended hepatectomy (70.0%) and a systematic lymphadenectomy (62.2%). The incidence of lymph node metastases (overall, 36.9%) increased with increased tumor size, with 24.4% of patients with a small IHC (diameter 643 cm) having N1 disease. Almost one-third of patients required an additional major procedure to obtain a R0 resection in 84.6% of the cases. In these patients, the median time of survival was 39 months, and the 5-year survival rate was 39.8%. Lymph node metastases (hazard ratio, 2.21; P < .001), multiple tumors (hazard ratio, 1.50; P = .009), and an elevated preoperative cancer antigen 19.9 level (hazard ratio, 1.62; P = .006) independently predicted an adverse prognosis. Conversely, survival was not influenced by the width of a negative resection margin (P = .61). The potential survival benefit of a lymphadenectomy was assessed with the therapeutic value index, which was calculated to be 5.9 points. CONCLUSIONS Survival rates after a hepatectomy with a curative intent for IHC at tertiary referral centers exceed the survival rates reported in most study series in single institutions, which strengthens the value of an aggressive approach to radical resection. Lymph node metastases and multiple tumors are associated with decreased survival rates, but they should not be considered selection criteria that prevent other patients from undergoing a potentially curative resection. Lymphadenectomy should be considered for all patients