Influence of progressive renal dysfunction in chronic heart failure

Chronic heart failure (CHF) is often associated with impaired renal function due to hypoperfusion. Such patients are very sensitive to changes in renal perfusion pressure, and may develop acute tubular necrosis if the pressure falls too far. The situation is complicated by the use of diuretics, ACE inhibitors and spironolactone, all of which may affect renal function and potassium balance. Chronic renal failure (CRF) may also be associated with fluid overload. Anaemia and hypertension in CRF contribute to the development of left ventricular hypertrophy (LVH), which carries a poor prognosis, so correction of these factors is important.

Isolation of a bone marrow-derived stem cell line with high proliferation potential and its application for preventing acute fatal liver failure

Transplantation of hepatocytes or hepatocyte-like cells of extrahepatic origin is a promising strategy for treatment of acute and chronic liver failure. We examined possible utility of hepatocyte-like cells induced from bone marrow cells for such a purpose. Clonal cell lines were established from the bone marrow of two different rat strains. One of these cell lines, rBM25/S3 cells, grew rapidly (doubling time, approximately 24 hours) without any appreciable changes in cell properties for at least 300 population doubling levels over a period of 300 days, keeping normal diploid karyotype. The cells expressed CD29, CD44, CD49b, CD90, vimentin, and fibronectin but not CD45, indicating that they are of mesenchymal cell origin. When plated on Matrigel with hepatocyte growth factor and fibroblast growth factor-4, the cells efficiently differentiated into hepatocyte-like cells that expressed albumin, cytochrome P450 (CYP) 1A1, CYP1A2, glucose 6-phosphatase, tryptophane-2,3-dioxygenase, tyrosine aminotransferase, hepatocyte nuclear factor (HNF)1 alpha, and HNF4alpha. Intrasplenic transplantation of the differentiated cells prevented fatal liver failure in 90%-hepatectomized rats. In conclusion, a clonal stem cell line derived from adult rat bone marrow could differentiate into hepatocyte-like cells, and transplantation of the differentiated cells could prevent fatal liver failure in 90%-hepatectomized rats. The present results indicate a promising strategy for treating human fatal liver diseases.

Numerical analysis of intralaminar failure mechanisms in composite structures, Part I: FE implementation

This paper presents a three-dimensional continuum damage mechanics-based material model which was implemented in an implicit finite element code to simulate the progressive intralaminar degradation of fibre reinforced laminates. The damage model is based on ply failure mechanisms and uses seven damage variables assigned to tensile, compressive and shear damage at a ply level. Non-linear behaviour and irreversibility were taken into account and modelled. Some issues on the numerical implementation of the damage model are discussed and solutions proposed. Applications of the methodology are presented in Part II

Numerical analysis of intralaminar failure mechanisms in composite structures, Part II: Applications

A three-dimensional continuum damage mechanics-based material model was implemented in an implicit Finite Element code to simulate the progressive intralaminar degradation of fibre reinforced laminates based on ply failure mechanisms. This paper presents some structural applications of the progressive failure model implemented. The focus is on the non-linear response of the shear failure mode and its interaction with other failure modes. Structural applications of the damage model show that the proposed model is able to reproduce failure loads and patterns observed experimentally.

A progressive failure model for composite laminates subjected to low velocity impact damage

This paper presents a 3-D failure model for predicting the dynamic material response of composite laminates under impact loading. The formulation is based on the Continuum Damage Mechanics (CDM) approach and enables the control of the energy dissipation associated with each failure mode regardless of mesh refinement and fracture plane orientation. Internal thermodynamically irreversible damage variables were defined in order to quantify damage concentration associated with each possible failure mode and predict the gradual stiffness reduction during the impact damage process. The material model has been implemented into LS-DYNA explicit finite element code within solid elements and it has proven to be capable of reproducing experimental results with good accuracy in terms of static/dynamic responses, absorbed energy and extent of damage.

Failure of thick-skinned stiffener runout sections loaded in uniaxial compression

Recent efforts towards the development of the next generation of large civil and military transport aircraft within the European community have provided new impetus for investigating the potential use of composite material in the primary structure. One concern in this development is the vulnerability of co-cured stiffened structures to through-thickness stresses at the skin-stiffener interfaces particularly in stiffener runout regions. These regions are an inevitable consequence of the requirement to terminate stiffeners at cutouts, rib intersections or other structural features which interrupt the stiffener load path. In this respect, thickerskinned components are more vulnerable than thin-skinned ones. This work presents an experimental and numerical study of the failure of thick-sectioned stiffener runout specimens loaded in uniaxial compression. The experiments revealed that failure was initiated at the edge of the runout and propagated across the skin-stiffener interface. High frictional forces at the edge of the runout were also deduced from a fractographic analysis and it is postulated that these forces may enhance the fracture toughness of the specimens. Finite element analysis using an efficient thick-shell element and the Virtual Crack Closure Technique was able to qualitatively predict the crack growth characteristics for each specimen

Initial failure of mechanically fastened joints with offset loading

In this preliminary study the initial failure of a bolted composite joint was investigated. The results of an experimental program using two simple beams bolted together with offset loading are presented. These test specimens were used to simulate a typical skin-spar attachment in a composite wing undergoing hydraulic shock. Initial failure was found to be due to a prying force induced at the outer sections of the joint leading to transverse shear failure.

The failure of generalized gradient approximations (GGAs) and meta-GGAs for the two-center three-electron bonds in He-2(+), (H2O)(2)(+), and (NH3)(2)(+)

The radical cations He-2(+) (H2O)(2)(+), and (NH3)(2)(+) with two-center three-electron A-A bonds are investigated at the configuration interaction (CI), accurate Kohn-Sham (KS), generalized gradient approximation (GGA), and meta-GGA levels. Assessment of seven different GGA and six meta-GGA methods shows that the A(2)(+) systems remain a difficult case for density functional theory (DFT). All methods tested consistently overestimate the stability of A(2)(+): the corresponding D-e errors decrease for more diffuse valence densities in the series He-2(+) > (H2O)(2)(+) > (NH3)(2)(+). Upon comparison to the energy terms of the accurate Kohn-Sham solutions, the approximate exchange functionals are found to be responsible for the errors of GGA-type methods, which characteristically overestimate the exchange in A(2)(+). These so-called exchange functionals implicitly use localized holes. Such localized holes do occur if there is left-right correlation, i.e., the exchange functionals then also describe nondynamical correlation. However, in the hemibonded A(2)(+) systems the typical molecular (left-right, nondynamical) correlation of the two-electron pair bond is absent. The nondynamical correlation built into the exchange functionals is then spurious and yields too low energies.