Fault tectonics and earthquake hazards in parts of southern California

The author has identified the following significant results. Four previously unknown faults were discovered in basement terrane of the Peninsular Ranges. These have been named the San Ysidro Creek fault, Thing Valley fault, Canyon City fault, and Warren Canyon fault. In addition fault gouge and breccia were recognized along the San Diego River fault. Study of features on Skylab imagery and review of geologic and seismic data suggest that the risk of a damaging earthquake is greater along the northwestern portion of the Elsinore fault than along the southeastern portion. Physiographic indicators of active faulting along the Garlock fault identifiable in Skylab imagery include scarps, linear ridges, shutter ridges, faceted ridges, linear valleys, undrained depressions and offset drainage. The following previously unrecognized fault segments are postulated for the Salton Trough Area: (1) An extension of a previously known fault in the San Andreas fault set located southeast of the Salton Sea; (2) An extension of the active San Jacinto fault zone along a tonal change in cultivated fields across Mexicali Valley ( the tonal change may represent different soil conditions along opposite sides of a fault). For the Skylab and LANDSAT images studied, pseudocolor transformations offer no advantages over the original images in the recognition of faults in Skylab and LANDSAT images. Alluvial deposits of different ages, a marble unit and iron oxide gossans of the Mojave Mining District are more readily differentiated on images prepared from ratios of individual bands of the S-192 multispectral scanner data. The San Andreas fault was also made more distinct in the 8/2 and 9/2 band ratios by enhancement of vegetation differences on opposite sides of the fault. Preliminary analysis indicates a significant earth resources potential for the discrimination of soil and rock types, including mineral alteration zones. This application should be actively pursued

Analysis of pseudocolor transformations of ERTS-1 images of Southern California area

The author has identified the following significant results. Representative faults and lineaments, natural features on the Mojave Desert, and cultural features of the southern California area were studied on ERTS-1 images. The relative appearances of the features were compared on a band 4 and 5 subtraction image, its pseudocolor transformation, and pseudocolor images of bands 4, 5, and 7. Selected features were also evaluated in a test given students at the University of California, Los Angeles. Observations and the test revealed no significant improvement in the ability to detect and locate faults and lineaments on the pseudocolor transformations. With the exception of dry lake surfaces, no enhancement of the features studied was observed on the bands 4 and 5 subtraction images. Geologic and geographic features characterized by minor tonal differences on relatively flat surfaces were enhanced on some of the pseudocolor images

Collecting single molecules with conventional optical tweezers

The size of particles which can be trapped in optical tweezers ranges from tens of nanometres to tens of micrometres. This size regime also includes large single molecules. Here we present experiments demonstrating that optical tweezers can be used to collect polyethylene oxide (PEO) molecules suspended in water. The molecules that accumulate in the focal volume do not aggregate and therefore represent a region of increased molecule concentration, which can be controlled by the trapping potential. We also present a model which relates the change in concentration to the trapping potential. Since many protein molecules have molecular weights for which this method is applicable the effect may be useful in assisting nucleation of protein crystals.Comment: 5 pages, 4 figure

Mie scattering by a charged dielectric particle

We study for a dielectric particle the effect of surplus electrons on the anomalous scattering of light arising from the transverse optical phonon resonance in the particle's dielectric constant. Excess electrons affect the polarizability of the particle by their phonon-limited conductivity, either in a surface layer (for negative electron affinity) or the conduction band (for positive electron affinity). We demonstrate that surplus electrons shift an extinction resonance in the infrared. This offers an optical way to measure the charge of the particle and thus to use it in a plasma as a minimally invasive electric probe.Comment: 5 pages, 5 figures, accepted manuscrip

Casimir Energy of a Spherical Shell

The Casimir energy for a conducting spherical shell of radius $a$ is computed using a direct mode summation approach. An essential ingredient is the implementation of a recently proposed method based on Cauchy's theorem for an evaluation of the eigenfrequencies of the system. It is shown, however, that this earlier calculation uses an improper set of modes to describe the waves exterior to the sphere. Upon making the necessary corrections and taking care to ensure that no mathematically ill-defined expressions occur, the technique is shown to leave numerical results unaltered while avoiding a longstanding criticism raised against earlier calculations of the Casimir energy.Comment: LaTeX, 14 pages, 1 figur

Comparative plasma catecholamine and hemodynamic responses to handgrip, cold pressor and supine bicycle exercise testing in normal subjects

Serial hemodynamic and plasma catecholamine responses were compared among 10 healthy men (27 ± 3 years) ( ± 1 standard deviation) during symptom-limited handgrip (33% maximal voluntary contraction for 4.4 ± 1.8 minutes), cold pressor testing (6 minutes) and symptom-limited supine bicycle exercise (22 ± 5 minutes). Plasma catecholamine concentrations were measured by radioenzymatic assays; ejection fraction and changes in cardiac volumes were assessed by equilibrium radionuclide angiography. During maximal supine exercise, plasma norepinephrine and epinephrine concentrations increased three to six times more than during either symptom-limited handgrip or cold pressor testing. Additionally, increases in heart rate, systolic blood pressure, rate-pressure product, stroke volume, ejection fraction and cardiac output were significantly greater during bicycle exercise than during the other two tests. A decrease in ejection fraction of 0.05 units or more was common in young normal subjects during the first 2 minutes of cold pressor testing (6 of 10 subjects) or at symptom-limited handgrip (3 of 10), but never occurred during maximal supine bicycle exercise.The magnitude of hemodynamic changes with maximal supine bicycle exercise was greater, more consistent and associated with much higher sympathetic nervous system activation, making this a potentially more useful diagnostic stress than either handgrip exercise or cold pressor testing

On the exact electric and magnetic fields of an electric dipole

We derive from Jefimenko's equations a multipole expansion in order to obtain the exact expressions for the electric and magnetic fields of an electric dipole with an arbitrary time dependence. A few comments are also made about the usual expositions found in most common undergraduate and graduate textbooks as well as in the literature on this topic

Inhibition of Overactive Transforming Growth Factor–β Signaling by Prostacyclin Analogs in Pulmonary Arterial Hypertension

YesHeterozygous loss of function mutations in the type II bone morphogenetic protein receptor (BMPR-II), a member of the transforming growth factor (TGF-β) receptor family, underlie the majority of familial cases of pulmonary arterial hypertension (PAH). The TGF-β1 pathway is activated in PAH and inhibitors of TGF-β1 signaling prevent the development and progression of PAH in experimental models. However, the effect of currently utilized therapies on the TGF-β pathway is not known. Prostacyclin analogues remain the first line of treatment for clinical PAH. We hypothesized that these agents effectively decrease the activity of the TGF-β1 pathway. Beraprost sodium (BPS), a prostacyclin analogue selectively inhibits proliferation in a dose-dependent manner in mouse primary pulmonary arterial smooth muscle cells (PASMCs) harbouring a pathogenic BMPR2 nonsense mutation in both the presence and absence of TGF-β1 stimulation. This study demonstrates that this agent inhibits TGF-β1–induced SMAD-dependent and -independent signaling via a PKA dependent pathway by reducing the phosphorylation of SMADs 2 and 3 and p38MAPK proteins. Finally, in a monocrotaline (MCT)-induced rat model of PAH, which is associated with increased TGF-β signaling, this study confirms that treprostinil (TPS), a stable prostacyclin analogue, inhibits the TGF-β pathway by reducing SMAD3 phosphorylation. Taken together, these data suggest that prostacyclin analogues inhibit dysregulated TGF-β signaling in vitro and in vivo and reduce BMPR-II-mediated proliferation defects in mutant mice PASMCs.The authors acknowledge financial support from the British Heart Foundation, United Kingdom (Programme Grant 1-2004-357 to R.C.T. and N.W.M.), a Heptagon Life Science Proof of Concept Fund (grants KCL24 and KCL25 to M.T.N. and R.C.T., respectively), and the Great Britain Sasakawa Foundation (grant B70 to M.T.N.

Diffraction of light by a planar aperture in a metallic screen

We present a complete derivation of the formula of Smythe [Phys.Rev.72, 1066 (1947)] giving the electromagnetic field diffracted by an aperture created in a perfectly conducting plane surface. The reasoning, valid for any excitating field and any hole shape, makes use only of the free scalar Green function for the Helmoltz equation without any reference to a Green dyadic formalism. We compare our proof with the one previously given by Jackson and connect our reasoning to the general Huygens Fresnel theorem.Comment: J. Math. Phys. 47, 072901 (2006

Rainbow scattering in the gravitational field of a compact object

We study the elastic scattering of a planar wave in the curved spacetime of a compact object such as a neutron star, via a heuristic model: a scalar field impinging upon a spherically symmetric uniform density star of radius R and mass M. For R<rc, there is a divergence in the deflection function at the light-ring radius rc ¼ 3GM=c2, which leads to spiral scattering (orbiting) and a backward glory; whereas for R>rc, there instead arises a stationary point in the deflection function which creates a caustic and rainbow scattering. As in nuclear rainbow scattering, there is an Airy-type oscillation on a Rutherford-like cross section, followed by a shadow zone. We show that, for R ∼ 3.5GM=c2, the rainbow angle lies close to 180°, and thus there arises enhanced backscattering and glory. We explore possible implications for gravitational wave astronomy and dark matter models