High frequency properties of a planar ion trap fabricated on a chip.

We report on the measurement of the high frequency properties of a planar Penning ion trap fabricated on a chip. Two types of chips have been measured: the first manufactured by photolithographic metal deposition on a p-doped silicon substrate and the second made with printed circuit board technology on an alumina substrate. The input capacitances and the admittances between the different trap's electrodes play a critical role in the electronic detection of the trapped particles. The measured input capacitances of the photolithographic chip amount to 65-76 pF, while the values for the printed circuit board chips are in the range of 3-5 pF. The latter are small enough for detecting non-destructively a single trapped electron or ion with a specifically tuned LC resonator. We have also measured a mutual capacitance of ∼85 fF between two of the trap's electrodes in the printed circuit board chip. This enables the detection of single, or very few, trapped particles in a broader range of charge-to-mass ratios with a simple resistor on the chip. We provide analytic calculations of the capacitances and discuss their origin and possible further reduction.

Carbon Chemistry in IRC+10216: Infrared Detection of Diacetylene.

We present the detection of C4H2 for first time in the envelope of the C-rich AGB star IRC+10216 based on high spectral resolution mid-IR observations carried out with the Texas Echelon-cross-Echelle Spectrograph (TEXES) mounted on the Infrared Telescope Facility (IRTF). The obtained spectrum contains 24 narrow absorption features above the detection limit identified as lines of the ro-vibrational C4H2 band ν6+ν8(σu+). The analysis of these lines through a ro-vibrational diagram indicates that the column density of C4H2 is (2.4 ± 1.5) × 1016 cm-2. Diacetylene is distributed in two excitation populations accounting for 20 and 80% of the total column density and with rotational temperatures of 47 ± 7 and 420 ± 120 K, respectively. This two-folded rotational temperature suggests that the absorbing gas is located beyond ≃0·"4≃20R⋆ from the star with a noticeable cold contribution outwards from ≃ 10″ ≃ 500R⋆. This outer shell matches up with the place where cyanoacetylenes and carbon chains are known to form due to the action of the Galactic dissociating radiation field on the neutral gas coming from the inner layers of the envelope.

The abundance of 28Si32S, 29Si32S, 28Si34S, and 30Si32S in the inner layers of the envelope of IRC+10216.

We present high spectral resolution mid-IR observations of SiS towards the C-rich AGB star IRC+10216 carried out with the Texas Echelon-cross-Echelle Spectrograph mounted on the NASA Infrared Telescope Facility. We have identified 204 ro-vibrational lines of 28Si32S, 26 of 29Si32S, 20 of 28Si34S, and 15 of 30Si32S in the frequency range 720 - 790 cm-1. These lines belong to bands v = 1 - 0, 2 - 1, 3 - 2, 4-3, and 5-4, and involve rotational levels with Jlow ≲ 90. About 30 per cent of these lines are unblended or weakly blended and can be partially or entirely fitted with a code developed to model the mid-IR emission of a spherically symmetric circumstellar envelope composed of expanding gas and dust. The observed lines trace the envelope at distances to the star ≲ 35R⋆(≃ 0″.7). The fits are compatible with an expansion velocity of 1+2.5(r/R⋆ -1) km s-1 between 1 and 5R⋆, 11 km s-1 between 5 and 20R⋆, and 14.5 km s-1 outwards. The derived abundance profile of 28Si32S with respect to H2 is 4.9 × 10-6 between the stellar photosphere and 5R⋆, decreasing linearly down to 1.6 × 10-6 at 20R⋆ and to 1.3 × 10-6 at 50R⋆. 28Si32S seems to be rotationally under LTE in the region of the envelope probed with our observations and vibrationally out of LTE in most of it. There is a red-shifted emission excess in the 28Si32S lines of band v = 1 - 0 that cannot be found in the lines of bands v = 2 - 1, 3 - 2, 4 - 3, and 5 - 4. This excess could be explained by an enhancement of the vibrational temperature around 20R⋆ behind the star. The derived isotopic ratios 28Si/29Si, and 32S/34S are 17 and 14, compatible with previous estimates.

Unraveling the 10 micron "silicate" feature of protostars: the detection of frozen interstellar ammonia.

We present infrared spectra of four embedded protostars in the 750-1230 cm-1 (13.3-8.1 microns) range. For NGC 7538 IRS 9, a new band is reported at 1110 cm-1 (9.01 microns, and several others may be present near 785, 820, 900, 1030, and 1075 cm-1 (12.7, 12.2, 11.1, 9.71, and 9.30 microns). The band 1110 cm-1 is attributed to frozen NH3. Its position and width imply that the NH3 is frozen in a polar, H2O-rich interstellar ice component. The NH3/H2O ice ratio inferred for NGC 7538 IRS 9 is 0.1, making NH3 as important a component as CH3OH and CO2 in the polar ices along this line of sight. At these concentrations, hydrogen bonding between the NH3 and H2O can account for much of the enigmatic low-frequency wing on the 3240 cm-1 (3.09 microns) H2O interstellar ice band. The strength of the implied NH3 deformation fundamental at 1624 cm-1 (6.158 microns) can also account for the absorption at this position reported by ISO.

Fabrication and evaluation of an etched infrared diffraction grating.

We evaluated the optical performance of an IR echelle grating produced on a silicon wafer with anisotropic etching techniques. We measured the diffraction efficiency of a sample with a 55° blaze angle and 25-µm groove spacing. We also calculated the efficiency for typical triangular and trapezoidal groove profiles of etched gratings. The diffraction efficiency for unpolarized light can be approximately as high as the efficiency of right-angle groove gratings. The great potential of the etched silicon grating lies in its ease of fabrication, its excellent surface quality, and the high reproducibility of the production process. Compact high-resolution diffraction gratings can be produced by etching the grating pattern into the rear side of a transparent prism. When used in internal reflection, this increases the resolving power of the grating by a factor equal to the refractive index of the prism over a front surface grating of the same length.

Use of plasma volume expanders in myocardial revascularisation.

The optimal solution for priming cardiopulmonary bypass machines and for postoperative resuscitation following myocardial revascularisation should be inexpensive, free of risk of transmitting disease, and free of other detrimental side effects. Colloid solutions are preferred over crystalloid solutions because of elevations in extracellular sodium and water that occur with cardiopulmonary bypass. Albumin, plasma protein solution, hetastarch (hydroxyethyl starch) and dextran are available for use if blood is not necessary and mediastinal blood is not available. Hetastarch is associated with a lower risk of bleeding and less risk of allergic reaction than dextran, and its cost is substantially less than that of albumin. However, high doses increase the risk of bleeding complications.

Pseudoaneurysm: diagnosis with color Doppler ultrasound.

Increasing numbers of interventional radiologic procedures, often with large arterial catheters, have led to increasing total numbers of complications. Pseudoaneurysm is not an infrequent complication. It is often difficult to differentiate pseudoaneurysm clinically from hematoma. In the past, we have used gray scale duplex scanning to aid in this differentiation. We have recently found color Doppler scanning to allow quicker, easier, and more accurate diagnosis. Color Doppler imaging also can often demonstrate the track between the artery and the aneurysm.

Elimination of mechanical failure of the Hickman right atrial catheter.

The double lumen Hickman right atrial catheter (Evermed Co., Palo Alto, Calif.) is usually inserted through an open venous cutdown into the internal jugular or cephalic vein. It is difficult to mechanically secure. Tight ligatures around the vein opening and catheter occlude the lumen of the Silastic rubber catheter while loose ligatures allow slippage. Migration of the tip into the vena cava or innominate vein causes fibrin sleeve formation and occlusion. Because of problems during the initial use of this catheter, we modified a subsequent series by placing a Silastic rubber bead on the catheter. The catheter is carefully trimmed so that the tip will lie in the right atrium and the bead is placed into the vein proximal to the securing ligature. Comparison of the two series of primarily leukemic patients revealed complete elimination of mechanical problems in patients with beaded catheters (0/18), and significant mechanical failure in unbeaded catheters (7/23). These data indicate that adequate fixation of the Hickman catheter at the level of the venotomy and placement of the tip in the right atrium eliminates mechanical failure and markedly improves catheter function.

Management of malignant ascites.

The management of malignant ascites is a significant clinical problem. Although most of the patients who have this complication develop have rather significantly limited life expectancy rates, they may be successfully palliated if appropriate steps are taken to provide them with the proper therapy. All of the aforementioned treatment modalities, specifically intracavitary radiotherapy, radioactive colloids, intracavitary chemotherapy, peritoneovenous shunting and immunotherapy have distinct advantages and limitations. With the proper selection of the modality to fit the individual patient, a relatively good result can be obtained, providing, of course, that proper care is taken to anticipate the potential complications, which occur frequently in the treatment of malignant effusion.