The influence of defects of the fatigue resistance of butt and girth welds in A106B steel

This three-phase study was directed at developing a fitness for service defect acceptance criteria for welds with defect indications. The study focussed on A106 Gr. B steel pipe. The first phase involved a literature search and critical review to develop the preliminary acceptance criteria to the extent permitted by the data. The second phase developed data for flat plate, wall segment, and vessel specimens containing artificial or natural planar or volumetric defects. The final phase developed acceptance criteria from the test data

Density and conductivity of bismuth single crystals grown in magnetic fields with relation to their mosaic structure

In continuation of the study of the thermoelectric effect, previously described by Goetz and Hasler, existing between the two halves of the same bismuth single crystal, of which one has been crystallized within, and the other outside of a strong magnetic field (21,000 gauss), the density and the specific resistance of different sections of these crystals, grown by the discontinuous method, have now been measured. The change of density of "magnetic" crystals. The density of perfect crystals grown under normal conditions was found to be between 9.82 and 9.83 i.e., 0.2 percent higher than the values of other authors. Furthermore, it was found that any crystalline imperfection such as twinning, etc., decreases the density; that, further there exists a difference of density between the "normal" and the "magnetic" half of the same crystal, the sign of which depends on the orientation with which the crystal entered the field: In case the trigonal axis is normal to the axis of the rod and normal to the lines of force, the "magnetic" half shows an increase of density, whereas the opposite is true in case the principal axis is parallel to the rod (and therefore parallel to the direction of growth and to the heat-flow). The difference of density is ca. 0.3 percent but can be several percent in imperfect crystals. The purity of the metal affects the change of the density. The results indicate that the ideally pure metal would not be affected by the magnetic treatment. The specific resistance of "magnetic" crystals. The values of the specific resistance obtained on "normal" single crystals agree approximately with the results obtained by Bridgman and Kapitza and also with those obtained by spectroscopic analysis. The value of ρ∥/ρ⊥ was found to be much larger for bismuth, being sensitive to the "magnetic" treatment. There is a small change of resistance between the normal and the magnetic half, depending on the orientation of the crystal to the field. In case the orientation is such as to decrease the density the resistance increases and vice versa. The accuracy necessary for the satisfactory quantitative determination of the change could not yet be reached, since the change is of the magnitude of 0.5 percent. An attempt is made to combine the phenomena of the magnetic effect thus far known. It seems probable that the influence of the magnetic field upon the formation of a crystal consists of a change within the mosaic structure of the lattice. The investigation is being continued

Approach to a rational rotation number in a piecewise isometric system

We study a parametric family of piecewise rotations of the torus, in the limit in which the rotation number approaches the rational value 1/4. There is a region of positive measure where the discontinuity set becomes dense in the limit; we prove that in this region the area occupied by stable periodic orbits remains positive. The main device is the construction of an induced map on a domain with vanishing measure; this map is the product of two involutions, and each involution preserves all its atoms. Dynamically, the composition of these involutions represents linking together two sector maps; this dynamical system features an orderly array of stable periodic orbits having a smooth parameter dependence, plus irregular contributions which become negligible in the limit.Comment: LaTeX, 57 pages with 13 figure

Calibration of the LIGO displacement actuators via laser frequency modulation

We present a frequency modulation technique for calibration of the displacement actuators of the LIGO 4-km-long interferometric gravitational-wave detectors. With the interferometer locked in a single-arm configuration, we modulate the frequency of the laser light, creating an effective length variation that we calibrate by measuring the amplitude of the frequency modulation. By simultaneously driving the voice coil actuators that control the length of the arm cavity, we calibrate the voice coil actuation coefficient with an estimated 1-sigma uncertainty of less than one percent. This technique enables a force-free, single-step actuator calibration using a displacement fiducial that is fundamentally different from those employed in other calibration methods.Comment: 10 pages, 5 figures, submitted to Classical and Quantum Gravit

RNA Interference by Production of Short Hairpin dsRNA in ES Cells, Their Differentiated Derivatives, and in Somatic Cell Lines

dsRNA of several hundred nucleotides in length is effective at interfering with gene expression in mouse oocytes, pre-implantation embryos, and embryonic stem (ES) cells but is not as efficient in differentiated cell lines. Here we describe a method to achieve RNA interference in totipotent and differentiated ES cells together with a wide range of other mammalian cell types that is both simple and efficient. It utilizes a linearized plasmid that directs the expression of a hairpin RNA with a 22-nucleotide-paired region. This molecule has a 13-nucleotide 5′ overhang that would be subject to capping on its 5′ phosphoryl group and thus differs from the ideal structure suggested for effective small interfering RNAs. Thus, it appears either that the structure of small inhibitory RNA molecules may not need to be as precise as previously thought or that such a transcript is efficiently processed to a form that is effective in interfering with gene expression