Frequency shifting of pulsed narrow-band laser light in a multipass Raman cell

A multipass cell is described which allows efficient stimulated Raman frequency shifting for low pump laser intensities and low gas pressures. The latter is important for Raman shifting of narrow-band Fourier-transform limited light pulses (Δv=75 MHz). It is shown that frequency broadening of the Raman shifted light can be largely avoided in the Dicke narrowing regime at low pressures. For 75 MHz pump pulses and an H2 density of 2.5 amagat we found a negligible broadening to 90 MHz of the stimulated Stokes light. This is far below the value of 250 MHz expected from spontaneous emission. The narrow-band Stokes pulses achieved in CO2 enabled us to measure the pressure shift coefficient (-0.71×10-2 cm-1/amagat) of this gas. It is demonstrated, for the example of benzene, that our technique provides a very practical light source for high resolution molecular spectroscopy

A prism reflector of anti-resonant ring configuration

Two identical prisms are combined to form an anti-resonant ring reflector, giving total reflection without the use of coatings or roof edges. When used as the total reflector in a Q-switched Nd:YAG laser this device has shown a damage threshold twice that of a multilayer reflector

CoFlo tray Design and Technology Report

This report consists of two major segments. CoFlo Tray Design is the first section. The objectives of this section are: (1) Determine the design requirements for increased capacity by the substitution of CoFlo trays for sieve trays in a 15-tray 46-inch diameter column. The Design Basis was obtained from the Separations Research Program, which was solicited by an industrial customer on the use of CoFlo trays for their application. (2) Illustrate the design procedures so that they can be computerized to rapidly provide design and cost information for future customers. A summary of the research studies on which each design procedure is based is included. (3) Compare the costs of new sieve tray and CoFlo tray columns for this application to illustrate the savings inherent in the CoFlo process. Exhibits are the second section of this report and its objectives are to: (a) Report the extensive research studies on the CoFlo tray and related items; (b) Analyze present and potential future performance of the CoFlo tray; (c) Present comparative costs for sieve and CoFlo tray columns; and (d) List the applications for the CoFlo deentrainer

Thin film conductors for self-equalizing cables

Self-equalizing cables using hollow conductors with wall thickness less than the skin depth were proposed in 1929. However, they do not appear ever to have been widely used, although the idea has resurfaced and been refined from time to time. In the early 2000’s, self-equalizing conductors consisting of solid magnetic steel cores coated with silver were developed by W.L. Gore, and used in their 2.5 Gb/s “Eye-Opener” cables, although higher speed versions never appeared. We have revived the original 1929 idea, proposing to use glass as a solid insulating core. This technology can potentially work at frequencies of many 10’s of GHz. Possible uses include short range GHz links such as USB and Thunderbolt, and intra-rack interconnections in data centers. Our feasibility experiments have validated the principle. Copper coated glass fibers can, in principle, be manufactured, but in these tests, the conductors were capillaries internally coated with silver as these are easily obtainable, relatively inexpensive and serve to test the concept. The performance of these experimental twin lead cables corresponds to calculations, confirming the general principle. By calculation, we have compared the performance of cables made from copper-on-insulator conductors to that of similar cables made with solid copper conductors, and verified that copper-on-insulator cables have significantly less frequency dependent loss. We have also made and tested cables with copper on PEEK conductors as surrogates for copper on glass fiber

Demonstration of complex shear wave patterns in skeletal muscle in vivo using 3D SWEI

Shear wave elastography imaging (SWEI) of skeletal muscle has previously been used to identify speeds along and across the fibers, with limited success and low repeatability. In this work we show how a tilted configuration can be used to fully characterize muscle as an elastic incompressible TI material using ultrasonic techniques. In the vastus lateralis of a healthy volunteer, a 3D rotational shear wave elastography imaging (SWEI) setup was used to identify shear wave speeds in all directions. Due to the inherent tilt of the muscle fibers relative to the transducer face, multiple shear wave fronts are created. In an elastic incompressible transversely isotropic (TI) material these are the shear vertical (SV) and shear horizontal (SH) mode. By measuring both wave modes and comparing to matched Green's function simulations, this work measures for the first time in vivo all three parameters necessary to fully characterize an elastic incompressible TI material

Full characterization of in vivo muscle as an elastic, incompressible, transversely isotropic material using ultrasonic rotational 3D shear wave elasticity imaging

Using a 3D rotational shear wave elasticity imaging (SWEI) setup, 3D shear wave data were acquired in the vastus lateralis of a healthy volunteer. The innate tilt between the transducer face and the muscle fibers results in the excitation of multiple shear wave modes, allowing for more complete characterization of muscle as an elastic, incompressible, transversely isotropic (ITI) material. The ability to measure both the shear vertical (SV) and shear horizontal (SH) wave speed allows for measurement of three independent parameters needed for full ITI material characterization: the longitudinal shear modulus μL, the transverse shear modulus μT, and the tensile anisotropy χE. Herein we develop and validate methodology to estimate these parameters and measure them in vivo, with μL = 5.77 ± 1.00 kPa, μT = 1.93 ± 0.41 kPa (giving shear anisotropy χμ = 2.11 ± 0.92), and χE = 4.67 ± 1.40 in a relaxed vastus lateralis muscle. We also demonstrate that 3D SWEI can be used to more accurately characterize muscle mechanical properties as compared to 2D SWEI