Wavelength selection for low-saturation pulse oximetry

Conventional pulse oximeters are accurate at high oxygen saturation under a variety of physiological conditions but show worsening accuracy at lower saturation (below 70%). Numerical modeling suggests that sensors fabricated with 735 and 890 nm emitters should read more accurately at low saturation under a variety of conditions than sensors made with conventionally used 660 and 900 nm band emitters. Recent animal testing confirms this expectation. It is postulated that the most repeatable and stable accuracy of the pulse oximeter occurs when the fractional change in photon path lengths due to perturbations in the tissue (relative to the conditions present during system calibration) is equivalent at the two wavelengths. Additionally, the penetration depth (and/or breadth) of the probing light needs to be well matched at the two wavelengths in order to minimize the effects of tissue heterogeneity. At high saturation these conditions are optimally met with 660 and 900 nm band emitters, while at low saturation 735 and 890 nm provide better performance     

Risk factors and outcome of human immunodeficiency virus-infected patients with sporadic multidrug-resistant tuberculosis in New York City

The discovery of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma has opened a potentially new therapeutic approach in this group of patients with a poor prognosis and few effective therapy modalities. Based on previous findings of increased uptake of 11C-5-hydroxytryptophan (11C-5-HTP) in neuroendocrine tumours using the PET technique, this tracer was applied in the study of 10 patients with metastatic hormone-refractory prostatic adenocarcinoma. In three patients, the study was repeated after treatment. An increased uptake of 11C-5-HTP was observed in all investigated skeletal lesions, although the magnitude of the uptake was moderate. The difference between the standard uptake values (SUV) in normal bone and metastatic lesions was significant (p < 0.001). A kinetic analysis of the uptake of 11C-5-HTP demonstrates an increase during the first minutes followed by a wash-out and a stabilization of the tissue/blood ratio at about 2. The Patlak plots demonstrated a gradual increase in the transport rate during the first 20 to 30 min, after which a constant level was observed. The SUV varied between patients and between lesions over time and treatment. The uptake of 11C-5-HTP discriminates metastatic lesions from normal bone and may thus aid in the diagnosis and, potentially, in treatment monitoring of metastatic hormone-refractory prostatic adenocarcinoma. Uptake kinetics are characterized by a wash-out and cannot alone be used as proof of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma.     

A patient with aortic dissection and abdominal aortic aneurysm with fistula

Aneurysm of the abdominal aorta is not uncommon in later life. The frequency of aneurysm rupture varies with aneurysm diameter. In rare cases, the aneurysm may rupture intra-abdominally into surrounding structures and give rise to a fistula. When blood vessels are involved, the commonest form is aortocaval fistula, the presenting symptoms being those of severe right-ventricular heart failure. Although thoracic aorta dissection may be made manifest in acute intense chest pain, it is asymptomatic in up to 50 per cent of cases. The article consists in a case report of asymptomatic thoracic aorta dissection occurring concomitantly with a ruptured abdominal aneurysm the symptoms of which were severe right ventricular heart failure due to an aortocaval fistula causing increased pressure, and severe bilateral oedema of the legs. If the rare complication of an aortocaval fistula could be detected earlier, it might be possible to prevent progression to refractory cardiac failure. The possibility of a fistula should be borne in mind if haematuria is present in a case of abdominal aneurysm or a pulsatile abdominal mass is present in conjunction with a murmur.     

Audemes at work: Investigating features of non-speech sounds to maximize content recognition

To access interactive systems, blind users can leverage their auditory senses by using non-speech sounds. The structure of existing non-speech sounds, however, is geared toward conveying atomic operations at the user interface (e.g., opening a file) rather than evoking broader, theme-based content typical of educational material (e.g., an historical event). To address this problem, we investigate audemes, a new category of non-speech sounds whose semiotic structure and flexibility open new horizons for the aural interaction with content-rich applications. Three experiments with blind participants examined the attributes of an audeme that most facilitate the accurate recognition of their meaning. A sequential concatenation of different sound types (music, sound effect) yielded the highest meaning recognition, whereas an overlapping arrangement of sounds of the same type (music, music) yielded the lowest meaning recognition. We discuss seven guidelines to design well-formed audemes.     

Myocardial turnover of endogenous opioids and calcitonin-gene-related peptide in the human heart and the effects of spinal cord stimulation on pacing-induced angina pectoris

OBJECTIVE: The authors determine if the intraoperative placement of paclitaxel powder in the subconjunctival space improves the outcome of glaucoma filtration surgery in rabbits. METHODS: A posterior lip sclerectomy was performed in the right eye of 24 New Zealand white rabbits. Before the conjunctiva was fully sutured, 8 mg of mannitol powder alone, or 8 mg of mannitol powder containing either 10 micrograms or 250 micrograms of paclitaxel, was placed in the subconjunctival space of six eyes each in masked fashion. An additional six animals were treated with episcleral application of a sponge soaked in a solution of 0.5 mg/ml of mitomycin C (MMC) for 5 minutes before the sclerectomy was performed. Intraocular pressure and bleb size were measured until the operation had failed or until the 7 weeks of observation had concluded. RESULTS: Both paclitaxel powder and MMC solution improved the outcome of filtration surgery in this model as measured by magnitude of intraocular pressure (IOP) lowering and duration of surgical success. No toxic effect of either drug was observed, although endophthalmitis was observed in eight animals followed for more than 3 weeks. CONCLUSION: The introduction of paclitaxel into the subconjunctival space at the conclusion of filtration surgery has an effect comparable to intraoperative MMC.     

Creating a community of inquiry in online environments: An exploratory study on the effect of a protocol on interactions within asynchronous discussions

The purpose of our research was to examine the influence of an online protocol on asynchronous discussions. A mixed-methods study compared two online graduate classes: one that used a protocol and one that did not use a protocol for the same discussion about a complex reading. Analysis of the data revealed that the online protocol more evenly distributed the presence of cognitive, social, and teaching elements necessary to create and sustain an online community of inquiry. Use of the protocol also promoted more shared group cognition and more student ownership of the discussion and empowered students to facilitate themselves, helping to reduce the instructor workload. These findings may enable educators to provide more dynamic interaction and richer learning experiences in asynchronous online environments.     

Varistor Performance of ZnO-Based Ceramics Related to Their Densification and Structural Development

Electrical potential barriers are often observed in ZnO-based ceramics. Earlier studies on ZnO photoconduction have shown that the narrow regions, where the sintered grains have grown together, control the resistance of the entire sample. In those regions, the surface/volume ratio is sufficiently high for the acceptor concentration (which occurs because of adsorbed oxygen) to exceed the donor concentration inside the ZnO grains. More recent works have shown that Schottky barriers result from interface states because of the chemisorbed oxygen ion at the ZnO-ceramic grain boundaries. The work reported in this paper involves the relationship between the densification of the microstructure and the varistor performance of ZnO ceramics. The emphasis of densification percentage as an indicator of the degree of sintering shows the desirability of continuity across ZnO grain boundaries, without the presence of voids or films of second phases, in optimizing varistor behavior. The effect of oxygen partial pressure on the development of varistor microstructure and electrical properties, as well the kinetics of grain growth, during the sintering process have been determined and are discussed.     

General method of phase analysis for individual multicomponent alloys

Construction of a complete phase diagram for a 5- (or higher-) component system is so timeconsuming as to be impractical at present. The usual type of information about the phases present, their compositions, and their amounts can be obtained for a particularC-component alloy by the present method:C is the number of components and may be as large as desired. The alloy is brought to an essentially equilibrium condition at the temperature of interest, and the compositions of the phases are determined by a suitable technique; for example, by electronbeam-microprobe analyses of the quenched specimen. The generalized lever law, in determinant form, is used to determine the amounts of the phases. Repetition of this analysis at a second temperature in the same phase region permits identification of the type of variant reaction (pseudoeutectic, and so forth) that is oçcurring. For invariant reactions, a technique such as quantitative metallography is employed to determine the amounts of the phases at an early and a late stage in the reaction. The type of reaction (eutectic, quasiperitectic, and so forth) can then be determined. From experimental data on alloy E an estimate can be made of two aspects of the behavior of a neighboring composition, alloy N; 1) liquidus temperature, and 2) invariant reaction. Thermodynamic procedures should permit useful extensions of the present method.