Electronic applications of high temperature superconductors

Over the last decade there have emerged many electronic applications of HTS technology which have important military as well as commercial implications. Examples of these include space communications, terrestrial wireless communications, radar, surveillance, countermeasures, medical applications and cryo-electronics. I will review many of the efforts in in this area that have been supported by the DoD which has invested over $350M on this technology. In addition I will discuss the efforts to develop cryocoolers to support the HTS technology.     

Designing collaborative,constructionist and contextual applications for handheld devices

This paper explores current applications for handheld devices and questions which of these make full use of the unique attributes of handheld devices in order to facilitate learning in a pedagogically sensible manner. In order to do so, the paper presents a functional framework which analyses handheld application in relation to their use as well as the pedagogical underpinning, if any, that informs their development. Our framework currently consists of seven distinct categories of application, which we term: administrative, referential, interactive, microworld, data collection, location aware and collaborative. We argue that three categories, namely data collection, location aware and collaborative, are particularly suited to learning with handheld devices when they are informed by collaborative, contextual and constructionist learning theories. Furthermore, we contend that applications of the type just outlined deserve further research since they are not attempting to replicate, or even augment, existing learning scenarios but rather they try to create new learning opportunities which would not be possible without (mobile) technology. Finally, the authors introduce a number of applications and learning scenarios that they have developed for handheld devices and explain their position within the framework.     

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20∶5n−3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18∶2n−6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n−3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2∶0.6∶1.0) than reference diets (P/M/S ratio 1∶1∶1) and this was true for both PE (33.4±1.0%vs 24.3±1.1%) and PC (9.3±0.5%vs 4.9±0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20∶5n−3 was preferentially incorporated into PE (10.8±0.2%, 6.0±0.02%) while smaller amounts were incorporated into PC (6.9±0.4%, 3.2±0.2%). The major n−3 polyunsaturated fatty acid found in PE in response to dietary 20∶5n−3 was the elongation metabolite 22∶5n−3 in both the atherogenic (17.7±0.7%) and reference (14.3±1.0%) dietary groups; 22∶6n−3 levels were less affected by diet (4.7±0.3% and 3.9±0.2%, respectively). The results can be interpreted to indicate an inverse relationship between the amount of dietary 18∶2n−6 and incorporation of 20∶5n−3 into erythrocyte membrane phospholipids regardless of whether the major dietary n−3 fatty acid was α-linolenate (18∶3n−3) or 20∶5n−3. This interpretation is supported by theoretical calculations.     

Predictability of healing of ischemic leg ulcers by radioisotopic and Doppler ultrasonic examination

In a prospective study of twenty-six patients with ischemic ulcerations of the lower extremity, the predictive reliability with regard to spontaneous wound healing of diabetes, pedal pulses, ankle blood pressure (ABP) as measured by doppler ultrasound, and "leg ulcer scan" as performed by the intra-arterial injection of radioactive albumin was evaluated. The results suggest that only the leg ulcer scan is significantly reliable in predicting the likelihood of spontaneous healing. The following format for the evaluation of the ischemic leg ulcer is therefore suggested: (1) If pedal pulses are present, a three week trial of conservative therapy is indicated before further evaluation. (2) If the doppler ABP is 50 mm Hg or less, the ulcer will not heal spontaneously. (3) Leg ulcer scan is indicated: (a) in the absence of pedal pulses if ABP is less than 50 mm Hg; (b) in the presence of pedal pulses if there is no evidence of spontaneous healing after three weeks of conservative therapy.     

Experimental and computational studies of bulk polymerization of styrene in the presence of N-(O-(1-phenylmethyl)oxy) phthalimide or cyclohexanone-O-(1-phenylmethyl)oxime

Summary Syntheses of potential initiators N-(O-(1-phenylethyl)oxy)phthalimide, N-(O-(1-phenylmethyl)oxy)phthalimide (POP), cyclohexanone-O-(1-phenylethyl)oxime, and cyclohexanone-O-(1-phenylmethyl)oxime (CHPO) are described. Bulk polymerization of styrene in the presence of POP or CHPO and molecular weight measurement by GPC indicate that the polymerization is not a living process. Ab initio calculations show that the C-O or O-N bond cleavage energies of POP and CHPO are close to each other (3: C-O: 46.4, O-N: 47.3 kcal/mol; 1: C-O: 46.9, O-N: 63.0 kcal/mol) and much higher than the similar analogs of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) (C-O: 20.9, O-N: 34.4 kcal/mol). The similar C-O and O-N bond cleavage energies of the synthesized initiators (POP/CHPO) indicate two possible cleavage pathways and may explain the non-living nature of the polymerization. These results may be helpful in finding future reversible terminator compounds for living polymerization. Received: 28 August 2000/Revised version: 5 December 2000/Accepted: 7 December 2000     

Fabrication and characterization of two-color midwavelength/long wavelength HgCdTe infrared detectors

High-performance 20-μm unit-cell two-color detectors using an n-p⁺-n HgCdTe triple-layer heterojunction (TLHJ) device architecture grown by molecular beam epitaxy (MBE) on (211)-oriented CdZnTe substrates with midwavelength (MW) infrared and long wavelength (LW) infrared spectral bands have been demonstrated. Detectors with nominal MW and LW cut-off wavelengths of 5.5 μm and 10.5 μm, respectively, exhibit 78 K LW performance with >70 % quantum efficiency, reverse bias dark currents below 300 pA, and RA products (zero field of view, 150-mV bias) in excess of 1×10³ Ωcm². Temperature-dependent current-voltage (I–V) detector measurements show diffusion-limited LW dark current performance extending to temperatures below 70 K with good operating bias stability (150 mV ± 50 mV). These results reflect the successful implementation of MBE-grown TLHJ detector designs and the introduction of advanced photolithography techniques with inductively coupled plasma (ICP) etching to achieve high aspect ratio mesa delineation of individual detector elements with benefits to detector performance. These detector improvements complement the development of high operability large format 640×480 and 1280×720 two-color HgCdTe infrared focal plane arrays (FPAs) to support third generation forward looking infrared (FLIR) systems.     

HgCdTe Growth on 6 cm × 6 cm CdZnTe Substrates for Large-Format Dual-Band Infrared Focal-Plane Arrays

This paper describes molecular-beam epitaxy growth of mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) dual-band device structures on large-area (6 cm × 6 cm) CdZnTe substrates. Wafer-level composition and defect mapping techniques were used to investigate the limiting mechanisms in improving the cutoff wavelength (λ _c) uniformity and reducing the defect density. Structural quality of epitaxial layers was monitored using etch pit density (EPD) measurements at various depths in the epitaxial layers. Finally, 640 × 480, 20-μm-pixel-pitch dual-band focal-plane arrays (FPAs) were fabricated to demonstrate the overall maturity of growth and fabrication processes of epitaxial layers. The MWIR/LWIR dual-band layers, at optimized growth conditions, show a λ _c variation of ±0.15 μm across a 6 cm × 6 cm CdZnTe substrate, a uniform low macrodefect density with an average of 1000 cm⁻², and an average EPD of 1.5 × 10⁵ cm⁻². FPAs fabricated using these layers show band 1 (MWIR) noise equivalent temperature difference (NETD) operability of 99.94% and band 2 (LWIR) NETD operability of 99.2%, which are among the highest reported to date.     

Predictors of smoking cessation among elderly smokers treated for nicotine dependence

OBJECTIVE: To examine outcomes and predictors of smoking cessation among elderly patients treated for nicotine dependence. DESIGN: Retrospective analysis of patients aged 65-82 who received a nicotine dependence consultation at the Mayo Medical Center between 1 April 1988 and 30 May 1992. Patients were contacted by telephone by a trained interviewer six months after the consultation and were sent a follow-up survey in August 1993. SETTING: Mayo Medical Center, Rochester, Minnesota, United States. SUBJECTS: A total of 613 patients (310 men, 303 women) with a mean age of 69.0 (SD 3.5) years were seen during the study period. MAIN OUTCOME MEASURES: Point prevalence self-reported smoking status. Patients were considered abstinent if they self- reported not smoking (not even a puff) during the seven days before contact. RESULTS: At six-month follow up, 24.8% of the 613 patients reported abstinence from smoking. On multivariate analysis, smoking abstinence was more likely if patients were hospitalised at the time of the consultation, married to a non-smoking spouse, very motivated to stop smoking, and reported their longest time of previous abstinence to be less than a day or more than a month. The response rate to the mailed follow-up survey was 69.9% (429 of 613). The mean duration of follow up was 40.0 +/- 13.2 months following the consultation. Of the 429 patients, 103 (24.0%) reported abstinence from smoking and 326 (76.0%) were smoking at six-month follow up. Patients who reported abstinence at six months had a higher cessation rate at the last follow up (76.0%) compared with patients who were smoking at six-month follow up (33.0%, P < 0.001). For patients who were not smoking at six months, no factors were found to significantly predict abstinence at last follow up. For patients who were smoking at six months, factors associated with smoking cessation at last follow up were: more than a year as the longest time off cigarettes before the consultation; counsellor rating of less severe nicotine dependence; and older age at first regular smoking. CONCLUSIONS: Several predictors of smoking cessation were identified in this study which may be useful for tailoring smoking interventions for the elderly.


     

Processed dietary plants demonstrate broad capacity for angiotensin converting enzyme and angiotensin II receptor binding inhibition in vitro

While the consumption of fruit and vegetables is protective against cardiovascular disease, the relative efficacy of specific plants is poorly substantiated. In addition, although most plants are consumed in a ‘processed’ state (i.e., including cooking), the bioactivity of processed forms of plants is also generally unknown. Effects on elements of the renin-angiotensin system (RAS) were studied in a selection of 131 dietary plant species, fungi or varietals, across 44 families, after standardised processing. Products were tested for in vitro inhibition of angiotensin converting enzyme (ACE) and of angiotensin II (AngII) binding to its receptor (AT₁R). The results indicated that ACE inhibition activity was weakly correlated with AngII to AT₁R inhibition and that ACE inhibitory activity was positively correlated with total polyphenolic content. These results highlight that processed forms of dietary plants exhibit broad capacity for in vitro modulation of RAS. Furthermore, considering the extensive ACE inhibitory activity reported for peptides derived from many dietary proteins, this implicates broad potential for RAS regulation by several dietary factors. With RAS elements also known to function in the gastro-intestinal (GI) tract, there is a need to understand the physiological role of dietary factors on GI function, blood pressure regulation and salt excretion.