Oval cell proliferation associated with the murine insertional mutation TgN737Rpw

The Tg737 gene was identified by its direct association with a transgene-induced insertion mutation in the mouse. This mutation causes pleiotropic phenotypes including a syndrome similar to autosomal recessive polycystic kidney disease in humans. This syndrome, in addition to renal cyst formation, includes the presence of an invariably associated liver abnormality. The liver pathology in TgN737Rpw mice is characterized by a biliary hyperplasia that includes the proliferation of cells that morphologically and immunologically resemble oval cells, a liver progenitor cell. This abnormality is first observed at approximately 5 days of age in the portal region and then progresses into the periportal regions. Additionally, the formation and proliferation of dysplastic ductular structures are observed from the onset of the phenotype. Serum chemistry indicated that the primary defect is likely to be of biliary origin, and hepatic function appears normal in the mutant mice. Therefore, this mutation is unlike other causes of oval cell proliferation in that the hepatic parenchyma is relatively unaffected. The identification of the Tg737 gene associated with this mutation suggests that it functions in regulating the proliferation/differentiation of oval cells within the liver, which further indicates that this gene may function in pathological conditions that include oval cell proliferation, such as hepatocellular carcinogenesis.     

Z-Beamlet: a multikilojoule, terawatt-class laser system

A large-aperture (30-cm) kilojoule-class Nd:glass laser system known as Z-Beamlet has been constructed to perform x-ray radiography of high-energy-density science experiments conducted on the Z facility at Sandia National Laboratories, Albuquerque, New Mexico. The laser, operating with typical pulse durations from 0.3 to 1.5 ns, employs a sequence of successively larger multipass amplifiers to achieve up to 3-kJ energy at 1054 nm. Large-aperture frequency conversion and long-distance beam transport can provide on-target energies of up to 1.5 kJ at 527 nm.     

Lowland Stream Restoration in Denmark: Background and Examples

Since 1982, Danish legislation on streams and drainage has included clauses which make it possible to implement river restoration. In this paper, the Danish shift in policy from drainage to the return of wetlands is described. To illustrate the new beginning on catchment management, two major river-restoration schemes, i.e. the River Brede demonstration project and the River Skjern Nature project, are presented. Both projects have been implemented and consist of many parts, including (a) returning the straight, regulated rivers back to their former meanders, (b) introducing better hydraulic interaction between the river and its meadows, and (c) establishing former lakes, bogs, ponds and marshes. Also, an increase in security against flooding has resulted, as the regulated 'water-motorways'have become more natural, with buffer-zones and retention of water in the restored features.     

A self-stabilizing quorum-based protocol for maxima computing

The goal of decentralized consensus protocols is to exchange information among nodes so that each node acquires the information held by every other node in the system. This paper presents a quorum-based, self-stabilizing maxima finding protocol which is based on a decentralized consensus protocol. The protocol exchanges information with less delay than existing ring-based, self-stablizing protocols. Furthermore, quorums can be composed, and the resulting composite quorums can be used to efficiently obtain a solution for any internetwork. Received: October 1999 / Accepted: June 2001     

A constitutive theory for rigid polyurethane foam

Rigid, closed-cell, polyurethane foam consists of interconnected polyurethane plates that form cells. When this foam is compressed, it exhibits an initial elastic regime, which is followed by a plateau regime in which the load required to compress the foam remains nearly constant. In the plateau regime, cell walls are damaged and large permanent volume changes are generated. As additional load is applied, cell walls are compressed against neighboring cell walls, and the stiffness of the foam increases and approaches a value equal to that of solid poyurethane. When the foam is loaded in tension, the cell walls are damaged and the foam fractures. A constitutive theory for rigid polyurethane foam has been developed. This theory is based on a decomposition of the foam in two parts: a skeleton and a nonlinear elastic continuum in parallel. The skeleton accounts for the foam behavior in the elastic and plateau regimes and is described using a coupled plasticity with continuum damage theory. The nonlinear elastic continuum accounts for the lock-up of the foam due to internal gas pressure and cell wall interactions. This new constitutive theory has been implemented in both static and dynamic finite element codes. Numerical simulations performed using the new constitutive theory are presented.     

Nonpoint N Runoff from Agricultural Watersheds into the Great Lakes

Eleven agricultural watersheds were continuously monitored for discharge and intensively sampled for runoff N, 1975-77, as part of the IJC Pollution from Land Use Activities Reference Group (PLUARG), Task Group C (Canadian). The watersheds, located in southern Ontario, were sampled between 30 to more than 500 times for NH₄-N, N0₃+N0₂-N, and total Kjeldahl N (TKN).The predominant chemical form of runoff N was N0₃-N with flow weighted concentration means on sampled days ranging from 0.57 to 5.62 mg/L. In contrast, TKN means ranged from 0.64 mg/L to 2.37 mg/L while average soluble NH₄-N concentrations varied from 0.03 mg/L to 0.60 mg/L. High runoff N0₃-N concentrations occurred from watersheds with extensive areas of tile drainage, row crops (especially com), and high kg/ha fertilizer N application rates. Elevated stream TKN concentrations were associated with watersheds with more impermeable soils.Stream N0₃-N loadings ranged from 2.1 ± 0.2 to 39.0 ± 7.6 kg N0₃-N/watershed ha. Significant N fertility losses in excess of 30 kg N0₃-N ha occurred from some watersheds, while other watersheds with extensive areas of hay and pasture and unimproved land gained more N0₃-N in precipitation than was lost as runoff. TKN loads averaged 32% and 25% of total N runoff for the 11 watersheds in 1975 and 1976 respectively. Efforts to reduce Ontario watershed N runoff should concentrate first on soluble N and therefore on improved efficiency of N fertilizer use on the extensive areas of tile drained corn in the lower Great Lakes basin. The effectiveness of standard soil erosion control methods, including grassed waterways and contour planting, should be investigated for reduction of TKN runoff.     

Ductile tearing predictions with Wellman’s failure model

Predictions for the Sandia National Laboratories fracture challenge (Boyce et al. in Int J Fract 2013) were generated using a transient dynamic finite element code with a multi-linear elastic plastic failure model developed by Wellman (Simple approach to modeling ductile failure. Sandia National Laboratories, Albuquerque 2012). This model is a conventional, rate independent, von Mises plasticity model for metals with user-prescribed hardening as a function of equivalent plastic strain. In addition to conventional plasticity, this model has empirical criteria for crack initiation and growth. Ductile tearing predictions generated with this model were found to be in good agreement with experimental measurements and observations.