The cryptic seismic potential of the Pichilemu blind fault in Chile revealed by off-fault geomorphology.

The first step towards assessing hazards in seismically active regions involves mapping capable faults and estimating their recurrence times. While the mapping of active faults is commonly based on distinct geologic and geomorphic features evident at the surface, mapping blind seismogenic faults is complicated by the absence of on-fault diagnostic features. Here we investigated the Pichilemu Fault in coastal Chile, unknown until it generated a Mw 7.0 earthquake in 2010. The lack of evident surface faulting suggests activity along a partly-hidden blind fault. We used off-fault deformed marine terraces to estimate a fault-slip rate of 0.52 ± 0.04 m/ka, which, when integrated with satellite geodesy suggests a 2.12 ± 0.2 ka recurrence time for Mw~7.0 normal-faulting earthquakes. We propose that extension in the Pichilemu region is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes, which has implications for assessing the seismic potential of cryptic faults along convergent margins and elsewhere.

Cytotoxic mechanism of XK469: resistance of topoisomerase IIbeta knockout cells and inhibition of topoisomerase I.

Topoisomerase IIbeta knockout mouse cells (beta-/-) were found to have only slight resistance to m-AMSA, a dual topoisomerase IIalpha-IIbeta poison, as compared to wild-type cells (beta+/+) during 1 h or 3 day exposures to the drug. In contrast, the beta-/- cells were greater than threefold resistant to XK469, a selective topoisomerase IIbeta poison during three day drug exposures (beta+/+ IC(50) = 175 microM, beta-/- IC(50) = 581 microM). Short term (1 h) exposure to XK469 was not cytotoxic to either beta-/- or beta+/+ cells, suggesting that anticancer therapy with XK469 may be more efficacious if systemic levels can be prolonged. During studies on topoisomerase activity in nuclear extracts of the beta+/+ and beta-/- cells, we found evidence that XK469 is a weak topoisomerase I catalytic inhibitor. The high IC(50) for topoisomerase I inhibition (2 mM) suggests that topoisomerase I is not a significant target for XK469 cytotoxicity.

Emission pattern of high-energy pions: A new probe for the early phase of heavy-Ion collisions

The emission pattern of charged pions has been measured in Au+Au collisions at 1 GeV/nucleon incident energy. In peripheral collisions and at target rapidities, high-energy pions are emitted preferentially towards the target spectator matter. In contrast, low-energy pions are emitted predominantly in the opposite direction. The corresponding azimuthal anisotropy is explained by the interaction of pions with projectile and target spectator matter. This interaction with the spectator matter causes an effective shadowing which varies with time during the reaction. Our observations show that high-energy pions stem from the early stage of the collision whereas low-energy pions freeze out later.

Signal processing of the echo signatures returned by submerged shells insonified by dolphin "clicks:" active classification.

A large set of dolphin-emitted acoustic pulses ("echolocation clicks") have been examined, which were reflected from various elastic shells that were suspended, underwater, 4.5 m in front of the animal in a large test site in Kaneohe Bay, Hawaii. A carefully instrumented analog-to-digital system continuously captured the emitted clicks and also the returned, backscattered echoes (A/D conversion at 500 kHz). Using standard conditioning techniques and food reinforces, the dolphin is taught to push an underwater paddle when the "correct" target-the one he has been trained to identify-is presented to him. He communicates his consistently correct identifying choices in this manner. Many echoes returned by three types of cylindrical shells in both the time and frequency domains as well as in the joint time-frequency (t-f) domain, by means of Wigner-type distributions have been examined. It will be shown exactly how specific features observable in these displays are directly related to the physical characteristics of the shells. This processing takes advantage of certain fundamental resonance principles to show which echo features contain information about the size, shape, wall thickness, and material composition of both the shell and its filler substance. In the same fashion that these resonance features give the identifying characteristics of each shell, it is believed they may also give them to the dolphin. These echo features may allow him to extract the target properties by inspection without any need for computations. It is claimed that this may be the fundamental physical explanation of the dolphin's amazing target ID feats, upon which they base their recognition choices. This claim may be substantiated by the detailed analysis of many typical echoes returned by various shells, when they are interrogated by several dolphins. Thus far, this analysis of many echoes from many shells has only been carried out for a single dolphin.

Phenylketonuria in South Africa. A report on the status quo.

During the 1980s a pilot newborn screening programme for the early detection (and treatment) of amino acidopathies, especially phenylketonuria (PKU), was conducted by the Department of National Health and Population Development. The motivation for this pilot programme was the high priority accorded PKU screening in Europe and North America and the presumed similarly high incidence of this condition among South Africans of European origin. From a cohort of 59,600 newborns screened in the Pretoria area over a period of 8 consecutive years (1979-1986), only 1 case of PKU (and 1 of tyrosinaemia) was found. Statistically this result is compatible (Poisson distribution, 95% confidence interval) with a 'true' incidence of not more than 3/59,600 (or about 1/20,000) newborns. It is concluded from this result and other relevant information that newborn screening for PKU and other amino acidopathies is not cost-effective and justifiable, especially against the background of prevailing demographic conditions and more pressing health priorities in South Africa. This particular screening programme was discontinued in 1986. The results and conclusions are presented here for the record.

Possible health effects of EMF.

In the last 15 years, a new environmental health concern has emerged: electric and magnetic fields (EMF) associated with 60 hertz (Hz), alternating current (AC) electricity. Because recent reports in the popular press have stirred public attention, patients may well ask their physicians about it. The Soviets were the first to speculate about health effects from electric fields in the early 1970s. Other studies followed throughout the '70s and '80s. Public debate has grown to include concerns about household electrical appliances.

Cloning of the cDNA encoding the myosin heavy chain of a vertebrate cellular myosin.

The complete amino acid sequence of a vertebrate cellular myosin heavy chain (MHC; 1,959 amino acids, 226 kDa) has been deduced by using cDNA clones from a chicken intestinal epithelial cell library. RNA blot analysis of kidney, spleen, brain, liver, and intestinal epithelial cells as well as smooth muscle cells from the aorta and gizzard indicates the presence of a 7.3-kilobase (kb) message that is larger than the message for chicken smooth and striated muscle MHC. The chicken intestinal epithelial cell MHC shows overall similarity in primary structure to other MHCs in the areas of the reactive thiol residues and in areas contributing to the ATP binding site and actin binding site. The globular head domain is followed by an alpha-helical coiled-coil region, and as in smooth muscle MHC there is a short uncoiled sequence at the carboxyl terminus of the molecule. Comparison of amino acid sequences in the rod regions between human and chicken cellular MHCs shows a remarkable 92% identity.

DNA replication and cell cycle control in Xenopus egg extracts.

Aspects of the regulation of DNA replication and mitosis have been studied using a cell-free extract of Xenopus eggs. The extract is characterized by repeated cycles of DNA replication and mitosis, which are accompanied by periodic synthesis and degradation of cyclins as well as fluctuations in the level of Histone H1 kinase activity. DNA replication in this system is dependent upon the formation of a nucleus. However, while nuclear structures are clearly required for initiation, a complete nuclear membrane does not appear to be necessary. Indirect immunofluorescence and DIC microscopy indicate that nuclear reformation from chromosomes occurs asynchronously around individual chromatids. Lamin polymerization, biotin-11-dUTP incorporation and association of polymerases with chromatin occur before membrane formation is complete. S phase nuclei are typified by the co-distribution of both anti-DNA polymerase alpha and anti-PCNA antibodies as discrete spots of fluorescence which align the chromatin. However, as DNA replication is terminated, PCNA fluorescence fades and DNA polymerase alpha dissociates from the chromatin and is redistributed throughout the nucleoplasm. By inhibiting DNA replication with aphidicolin, both DNA polymerase alpha and PCNA remain associated with the chromatin throughout prolonged incubation. Under these conditions mitosis is delayed by up to 70 min, although both the general rate of protein synthesis and more importantly the rate of cyclin synthesis and histone kinase activation are unaffected. Upon nuclear envelope breakdown and lamin dispersal, cyclins degrade; however, no chromosomes are formed, and both PCNA and DNA polymerase alpha remain associated with the chromatin. Also, histone kinase activity is maintained at elevated levels.