At least 13 times during the Pleistocene Epoch lava flowed into the inner gorge of the Grand Canyon and formed lava dams, as high as 600 m, that temporarily blocked the flow of the Colorado River. K-Ar ages on these lava dams indicate that the seven youngest formed within a short period of time between about 0.6 and 0.4 mega-annum (Ma). The physiography of the lava dam remnants within the canyo...

It has long been recognized that flood protection provided by levees is a double-edged sword. On one hand, levee systems have provided flood protection. On the other hand, given enough time levees either will be overtopped or will fail—leading to severe flood impacts on an unsuspecting population. Unlike a natural flood, levee failure flooding is often rapid, forceful, extremely damaging, and o...

For a given minimum cost of the electricity dispatch, multiple equivalent dispatch solutions may exist. We explore the sensitivity of networks to these dispatch solutions and their impact on the vulnerability of the network to cascading failure blackouts. It is shown that, depending on the heterogeneity of the network structure, the blackout statistics can be sensitive to the dispatch solution ...

While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958-1978); slight accumulation (1978-1997), slight erosion (1997-200...

for Acute Pulmonary Embolism To the Editor: We read with great interest a review paper titled “Acute Pulmonary Embolism, Part II: Risk Stratification, Treatment, and Prevention” by Goldhaber and associates in the December 2003 issue of the journal.1 The strategies for acute pulmonary embolism in their review are anticoagulation, inferior vena caval filters, thrombolysis, and embolectomy. They m...

From an ethical perspective, good governance involves the translation of collective moral intentions into effective and accountable institutional actions. With respect to the use of human subjects in Canadian health research, I contend that there have been many good intentions but very little in the way of appropriate governance arrangements. Hence, the question, "who minds the store?" is espec...

In this paper the Regge pole model is applied to K*(890) photoproduction. Conspiracy relations, kinematic constraints, factorization, and the question of when to set m y = 0 are discussed. Predictions are obtained, in the limit of large s and small t, for ?a , the density matrix, and the K* decay angular distribution. (To be submitted to Physical Review) * Work supported by U. S. Atomic Energy ...

Although evolutionary change within most species is thought to occur slowly, recent studies have identified cases where evolutionary change has apparently occurred over a few generations. Anthropogenically altered environments appear particularly open to rapid evolutionary change over comparatively short time scales. Here, we consider a Pacific salmon population that may have experienced life-h...

We simulate fragmentation and gravitational collapse of cold, magnetized molecular clouds. We explore the nonlinear development of an instability mediated by ambipolar diffusion, in which the collapse rate is intermediate to fast gravitational collapse and slow quasistatic collapse. Initially uniform stable clouds fragment into elongated clumps with masses largely determined by the cloud temper...

We review here some recent developments on the issue of final fate of gravitational collapse within the framework of Einstein theory of gravity. The structure of collapsed object is discussed in terms of either a black hole or a singularity having causal connection with outside universe. Implications for cosmic censorship are discussed.