Large Angle Optical Access in a Sub-Kelvin Cryostat.

The development of lens-antenna-coupled aluminum-based microwave kinetic inductance detectors (MKIDs) and on-chip spectrometers needs a dedicated cryogenic setup to measure the beam patterns of the lens-antenna system over a large angular throughput and broad frequency range. This requires a careful design since the MKID has to be cooled to temperatures below 300 mK to operate effectively. We developed such a cryostat with a large opening angle θ = ± 37 . 8 ∘ and an optical access with a low-pass edge at 950 GHz . The system is based upon a commercial pulse tube cooled 3 K system with a 4 He - 3 He sorption cooler to allow base temperatures below 300 mK . A careful study of the spectral and geometric throughput was performed to minimize thermal loading on the cold stage, allowing a base temperature of 265 mK . Radio-transparent multi-layer-insulation was employed as a recent development in filter technology to efficiently block near-infrared radiation.

Superconducting Coplanar Waveguide Filters for Submillimeter Wave On-Chip Filterbank Spectrometers.

We show the first experimental results which prove that superconducting NbTiN coplanar-waveguide resonators can achieve a loaded Q factor in excess of 800 in the 350 GHz band. These resonators can be used as narrow band pass filters for on-chip filter bank spectrometers for astronomy. Moreover, the low-loss coplanar waveguide technology provides an interesting alternative to microstrip lines for constructing large scale submillimeter wave electronics in general.

Number fluctuations of sparse quasiparticles in a superconductor.

We have directly measured quasiparticle number fluctuations in a thin film superconducting Al resonator in thermal equilibrium. The spectrum of these fluctuations provides a measure of both the density and the lifetime of the quasiparticles. We observe that the quasiparticle density decreases exponentially with decreasing temperature, as theoretically predicted, but saturates below 160 mK to 25-55/µm(3). We show that this saturation is consistent with the measured saturation in the quasiparticle lifetime, which also explains similar observations in qubit decoherence times.

Evaluation of image quality and radiation dose in adolescent thoracic imaging: 64-slice is preferable to 16-slice multislice CT.

There is a constant drive for radiology departments to acquire newer and improved CT machines in order to facilitate faster procedures and a greater repertoire of examinations. However, it is unclear whether the newer technology provides significantly improved image quality, or carries radiation dose implications for patients during everyday clinical practice. We assessed image quality and radiation dose in 15 children and young adults aged 9.3-19.5 years who underwent thoracic imaging on both 16-slice (16CT) and 64-slice (64CT) CT machines. Images were assessed for image quality on a visual analogue scale (1 = unacceptable; 5 = perfect) and preferred image set. All datasets were diagnostically acceptable (scores of 3 or more). The scores for 64CT datasets were significantly better than for 16CT datasets (mean scores of 4.5 and 4.0, respectively; p<0.05). The mean dose-length product (DLP) given was significantly higher during 16CT examinations at 152 mGy cm (effective dose, 2.1 mSv) than for 64CT examinations at 136 mGy cm (1.9 mSv; p<0.05). On average, 64CT examination DLPs were 16 mGy cm (or 9%) lower than the equivalent 16CT examination DLPs. In the context of childhood and adolescent thoracic CT imaging, and using the same software from the same manufacturers, 64CT examinations provide better image quality and give a lower effective dose than do 16CT examinations. If the choice were available, it would be pertinent to use 64CT for this patient group.

Quasiparticle relaxation in optically excited high-Q superconducting resonators.

The quasiparticle relaxation time in superconducting films has been measured as a function of temperature using the response of the complex conductivity to photon flux. For tantalum and aluminum, chosen for their difference in electron-phonon coupling strength, we find that at high temperatures the relaxation time increases with decreasing temperature, as expected for electron-phonon interaction. At low temperatures we find in both superconducting materials a saturation of the relaxation time, suggesting the presence of a second relaxation channel not due to electron-phonon interaction.

Use of quantum-point-contact high-electron-mobility-transistors for time domain multiplexing of large arrays of high impedance low temperature bolometers.

The use of a multiplexing readout for an array of bolometers simplifies the electronics and wiring, so making the readout of large arrays of bolometers (>100) feasible. Here we describe a time domain multiplexing technique and its performance based on the use of quantum-point-contact high-electron-mobility-transistors as low temperature (to approximately 100 mK) switches for measuring high impedance (5...70 MOmega) resistances and sensors. The presented system is well matched to ground based millimetric astronomy demands.

16-detector multislice CT: dosimetry estimation by TLD measurement compared with Monte Carlo simulation.

Computer simulations are widely used to estimate effective doses from CT examinations. The raw data often used in their estimations were obtained some years ago and made certain assumptions regarding CT unit design. At that time multidetector CT units were unavailable. Changes in design will limit the accuracy of computer simulated dosimetry on these machines. We therefore estimated CT dose on a 16-detector unit directly using thermoluminescent dosemeters (TLDs) and an anthropomorphic phantom. We found that the dose measured directly was 18% higher than the computer simulated dosimetry, in keeping with the previously recognised underestimation by computer simulation techniques compared with TLD measurements.

Effect of multislice scanners on patient dose from routine CT examinations in East Anglia.

As part of the dose optimization process, the Ionising Radiation (Medical Exposure) Regulations 2000 include requirements relating to the assessment of patient dose, and the setting and subsequent review of diagnostic reference levels. In East Anglia, audits of effective dose in CT have been carried out in 1996, 1999 and 2002. In the 2002 audit, nine of the 14 scanners assessed had been replaced since the previous audit. Eight of the new scanners were multislice scanners, acquiring up to 16 slices in a single rotation. The objective of the 2002 audit was to investigate the effect of the introduction of these multislice scanners on patient doses from routine CT examinations. Exposure parameters were collected for 10 different types of routine CT examination. In excess of 550 sets of patient data were obtained. For each of these, effective doses were calculated using the results of Monte Carlo simulations published by the National Radiological Protection Board. Averaged across all 10 examinations, regional mean effective doses are 34% higher than in 1999. The multislice scanners in the region give, on average, 35% more effective dose than the single-slice scanners. The effect of collimation in multislice scanners makes these effective dose differences most notable for examinations that use narrow slice widths. Further optimization of exposures on multislice scanners has the potential to reduce the differences observed between single-slice and multislice doses. However, when taken in combination with the increased use of CT in many hospitals, the effective dose increases observed are likely to result in a significant increase in the already substantial collective radiation dose from CT.

Heavy quasiparticles in the ferromagnetic superconductor ZrZn2.

We report a study of the de Haas-van Alphen effect in the normal state of the ferromagnetic superconductor ZrZn2. Our results are generally consistent with a linear muffin-tin orbital band structure which predicts four exchange-split Fermi surface sheets. Quasiparticle effective masses are enhanced by a factor of 4.9 implying a strong coupling to magnetic excitations or phonons. ZrZn2 is unique among metallic ferromagnets in that it has a very large density of states in the ferromagnetic phase.

Rechallenge of patients who had discontinued alendronate therapy because of upper gastrointestinal symptoms.

BACKGROUND: There have been reports from physicians in clinical practice that up to 30% of patients taking bisphosphonate therapy develop upper gastrointestinal (UGI) symptoms, many or most of which they assume to be related to the drug. However, in several large placebo-controlled clinical trials of bisphosphonates, the incidence of UGI symptoms has been > or =30%, even among patients receiving placebo, perhaps reflecting a high background incidence of UGI events in osteoporotic patients. OBJECTIVE: To assess the relationship between alendronate treatment and UGI complaints in patients who had discontinued treatment with alendronate in clinical practice because of UGI symptoms, we compared the incidence of such events on rechallenge with alendronate or placebo. METHODS: This was a multicenter, double-blind trial in which postmenopausal women with osteoporosis who had previously discontinued alendronate therapy because of a UGI adverse experience were randomized to daily treatment with either alendronate 10 mg or matching placebo (1:1 ratio) for 8 weeks. The primary end point was the cumulative incidence of discontinuations due to any UGI adverse experience. Secondary end points were the incidence of any clinical adverse experiences and the percentage change from baseline in urinary N-telopeptide adjusted for urinary creatinine at week 8. RESULTS: A total of 172 women were included in the study. They were a mean of 20.9 years past menopause, ranging in age from 41 to 90 years (mean, 67.0 years); 90.7% were white. On rechallenge, 14.8% (13/88) of patients in the alendronate group and 16.7% (14/84) in the placebo group discontinued treatment because of UGI adverse experiences. CONCLUSION: The results of this study suggest that many UGI adverse experiences reported during therapy with alendronate may reflect a high background incidence of UGI complaints and an increased sensitivity to detection of such complaints, rather than a causal relationship to therapy.

Diagnosis of maternal cystic fibrosis during pregnancy.

The third and fourth cases of maternal cystic fibrosis diagnosed during pregnancy are presented. Quantitative pilocarpine iontophoresis (sweat chlorides) must be performed to establish the diagnosis. Other important findings include recurrent or persistent respiratory symptoms, chest x-ray abnormalities, abnormal pulmonary function studies, and abnormal arterial blood gases. Gastrointestinal tract dysfunction and a positive family history for respiratory disease also suggest the diagnosis. Pregnant patients with cystic fibrosis require careful and frequent cardiopulmonary and gastrointestinal surveillance. A higher incidence of premature labor is noted and all patients are best managed in tertiary referral centers. Patients should also be monitored carefully during the puerperium because maternal pulmonary decompensation may occur during this time.

Primary epidermoid carcinoma of the vulva.

During a 12 year period, 102 patients with invasive epidermoid carcinoma of the vulva were treated at the University of Iowa Hospitals and Clinic. The over-all corrected three year survival rate was 65.5 per cent, or 67 of 102 patients. Those treated by radical vulvectomy and bilateral dissection of groin nodes had a three year survival rate of 76.9 per cent, or 40 of 52 patients, while those treated by radiotherapy had a survival rate of 10 per cent, or two of 20 patients. Those with Stage I disease lesions, less than 1 centimeter in diameter, had an excellent survival rate whether they were treated by vulvectomy only or by radical vulvectomy with groin node dissection. Our experience in this selected group of patients would indicate that a degree of individualization in the treatment of early invasive lesions of the vulva can give most satisfactory results.