Subclavian venogram as a guide to lead implantation

Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator and suppressed acutely by light. To identify photoreceptor mechanisms involved in the acute suppression of melatonin synthesis, an action spectrum was measured for dark-adapted Xenopus laevis eyecups at night. Intensity-response curves at six wavelengths from 400 to 650 nm were parallel, suggesting that a single photopigment predominates in melatonin suppression. Half-saturating intensities at 400, 440, 480, and 533 nm were not significantly different from one another, at 1-2 x 10(8) quanta cm(-2) s(-1). Significantly higher intensities of 580- and 650-nm light were required for melatonin suppression. These results indicate a predominant role for the principal green-absorbing rods in acute regulation of retinal melatonin synthesis in response to light, and argue against an important role for the red-absorbing cones. Higher than expected sensitivity at short wavelengths suggests that photoreceptors sensitive to blue and/or violet light may also contribute to melatonin suppression.     

Phase development and pore stability of yttria- and ytterbia-stabilized zirconia aerogels

High-porosity yttria- and ytterbia-stabilized zirconia aerogels offer the potential of extremely low thermal conductivity materials for high-temperature applications. Yttria- and ytterbia-doped zirconia aerogels were synthesized using a sol-gel approach over the dopant range of 0-20 atomic percent. Surface area, pore volume, and morphology of the as-dried aerogels and materials thermally exposed for short periods of time to temperatures up to 1200°C were characterized by nitrogen physisorption, scanning and transmission electron microscopy, and X-ray diffraction. The aerogels as supercritically dried all were X-ray amorphous. At a 5% dopant level, a tetragonal structure with a smaller monoclinic phase developed on thermal exposure. Mixed tetragonal and cubic phases or predominantly cubic materials were observed at higher dopant levels, depending on the dopant level, temperature and exposure time. The formation of crystalline phases was accompanied by loss of surface area and pore volume, although some mesoporous structure was maintained on short-term exposure to 1000°C. Incorporation of the smaller Yb atom into the lattice structure resulted in smaller lattice dimensions on crystallization than was seen with Y doping and favored a more highly equiaxed structure. Aerogels synthesized with 15% Y maintained the smallest particle size without evidence of sintering at 1100°C. Largest shrinkage and loss of pore volume occurred on crystallization from the amorphous phase, with further loss of pores at temperatures above 1000°C attributable to changes in lattice parameters.     

Off-axis tensile properties and fracture in a unidirectional graphite/polyimide composite (celion 6000/PMR 15)

Tensile properties of unidirectional Celion 6000 graphite/PMR 15 polyimide composites prepared by hot molding and cold molding processes were measured at room temperature and 316°C, the upper use temperature of the polyimide resin, at both 45 and 90° to the fiber axis. The resulting fractures were characterized by scanning electron microscopy and materialographic techniques. Variation in tensile properties with processing history occurred in the elastic modulus and strain to failure for specimens loaded at 90° at 316°C, and in the fracture stress, and hence the in-plane shear stress, for those loaded at 45° at room temperature. Significant plastic deformation was observed in the 45° orientation at 316°C for material produced by both processing methods. In general, fracture occurred by both failure within the matrix and at the fiber-matrix interface; the degree of interfacial failure increased with temperature. Secondary cracking below the primary fracture surface also was observed.     

Forced torsional properties of PMR composites with varying nadic ester concentrations and processing histories

PMR polyimide resin was prepared from 4,4′-methylenedianiline (MDA), the dimethyl ester of 3,3′,4,4′- benzophenonetetracarboxylic acid (BTDE) and the monomethyl ester of 5-norbornene-2,3-dicarboxylic acid (NE). The NE group serves as a chain terminator and crosslinking site. PMR/Celion 6000 composites were fabricated from resins having varying NE concentrations using two molding processes, and the laminates characterized in forced torsion. Glass transition temperatures (T_g) of 360–390°C were observed in the crosslinked resins, as compared with the literature value of 284°C reported for the uncrosslinked systemT_g did not decrease with decreasing NE concentrations over the range from 2.0 to 1.25 moles. Stoichiometry, within the range studied, showed little influence on shear properties; however, a 25% variation in matrix shear modulus with processing was observed. The G₁₂ values determined in forced torsion were in excellent agreement with those reported from tensile tests of ±45° laminates. A branching and possible secondary crosslink mechanism is proposed based on dynamic mechanical behavior and infrared spectra of the composites.     

Dual,Site‐Specific Modification of Antibodies by Using Solid‐Phase Immobilized Microbial Transglutaminase

Microbial transglutaminase (MTG) was stably solid‐phase immobilized on glass microbeads by using a second‐generation dendronized polymer. Immobilized MTG enabled the efficient generation of site‐specifically conjugated proteins, including antibody fragments, as well as whole antibodies through distinct glutamines and, unprecedentedly, also through lysines with various bifunctional substrates with defined stoichiometries. With this method, we generated dual, site‐specifically modified antibodies comprising a fluorescent probe and a metal chelator for radiolabeling—a strategy anticipated to design antibodies for imaging and simultaneous therapy. Furthermore, we provide evidence that immobilized MTG features higher siteselectivity than soluble MTG.     

Extreme-ultraviolet calibration of thin-film Zr filters for the cosmic hot interstellar plasma spectrometer

The design and calibration of thin-film Zr transmission filters for the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spaceborne astronomical telescope is presented. The transmission of a 1,000-A-thick Zr filter is measured for wavelengths from 45 to 1,304 A as well as its variability with respect to expected space-flight enviromental extremes of temperature, vibration, and atomic O bombardment. For the CHIPS spectral band of 90-260 A, the transmission of the Zr fiter is deemed useful between 90 and 200 A and is stable with respect to expected temperature and vibrational changes. The maximum atomic O bombardment decreases the filter transmission between 90 and 130 A by approximately 20% and does not appreciably affect the rest of the CHIPS bandpass. These results make Zr an acceptable filter candidate for CHIPS.     

Experience with reduction mammaplasty following breast conservation surgery and radiation therapy

Little is known about the outcome of breast reduction in the previously radiated breast. With the increased popularity of breast conservation in the management of breast cancer, it is inevitable that more women with breast cancer who have had a breast radiated will be seeking breast reduction. Although it would be expected that reduction of the radiated breast would be more challenging and would yield less-pleasing results, it has been unclear whether reduction in the radiated breast could be safely performed without interfering with mammography and cancer surveillance. Our experience using different techniques in three patients demonstrates that such reductions can be effectively and safely done if certain principles are followed. Pedicles should be designed to be broader and shorter than usual, and breast flaps should be undermined or elevated either minimally or not at all.     

Minimizing complications of ultrasound-assisted lipoplasty: an initial experience with no related complications

Numerous complications and increased operating times were reported with ultrasonically assisted lipoplasty in the first several months after introduction of the technology in the United States. The purpose of this study was to review early reported complications and management regimens, evaluate possible causes of problems, and apply indications and techniques to attempt to minimize complications during an initial experience with this technique beginning in January of 1997. Seven specific indications and modifications of existing techniques were developed and applied to an initial clinical series of 70 consecutive patients who underwent ultrasound-assisted suction lipoplasty between January 10, 1997, and August 1, 1997. Follow-up ranged from 1 to 7 months. No perioperative or postoperative complication occurred in any patient in this series. In this series of ultrasound-assisted lipoplasty cases, application of the following criteria resulted in a series of 70 patients with 1 to 7-month follow-up without complications: (1) selecting patients with well localized fat deposits who were no more than 20 percent above their ideal body weight; (2) infusing a solution of Ringer's Lactate containing 1 cc of 1:1000 epinephrine per 1000 cc into the area of fat removal, stopping infusion when the tissues first become firm, not infusing to marked tissue turgor or skin induration; (3) restricting the level of energy application to a minimum of 1 cm from the undersurface of the dermis; (4) limiting ultrasonic energy application in each area to approximately 1 minute per estimated 100 cc of total aspirate in a wet to superwet environment; (5) not performing ultrasound-assisted lipoplasty in the same area as another procedure that could potentially compromise tissue vascularity; (6) using a Lysonix 2000 generator and 5-mm golf tee tip probe at a power setting of 8 to apply ultrasonic energy to the area of fat removal, ceasing energy application when tissue resistance to the passage of the probe decreases and moving the cannula as rapidly as tissue resistance allows; and (7) using a standard elastic garment without adherent foam or other materials for 2 weeks postoperatively, encouraging all normal activity immediately, and restricting aerobic activities for 2 weeks.     

The pediatric airway. 1962

Stroke is the third leading cause of death in the United States. Carotid artery stenting is being investigated as a therapeutic strategy for the management of extracranial bifurcation stenosis and has the potential to prevent stroke in thousands of patients. Carotid endarterectomy, although effective, does have limitations, and percutaneous techniques may offer an alternative method of treatment, especially for those who are at highest risk. Although the technique is still evolving, this article describes the protocol and technique of stent-supported carotid angioplasty and care for patients undergoing this procedure at Washington Adventist Hospital in Takoma Park, MD.