The design of RIP belts impacts the reliability and quality of the measured respiratory signals.

PURPOSE: Evaluate the effect of respiratory inductance plethysmography (RIP) belt design on the reliability and quality of respiratory signals. A comparison of cannula flow to disposable cut-to-fit, semi-disposable folding and disposable RIP belts was performed in clinical home sleep apnea testing (HSAT) studies. METHODS: This was a retrospective study using clinical HSAT studies. The signal reliability of cannula, thorax, and abdomen RIP belts was determined by automatically identifying periods during which the signals did not represent respiratory airflow and breathing movements. Results were verified by manual scoring. RIP flow quality was determined by examining the correlation between the RIP flow and cannula flow when both signals were considered reliable. RESULTS: Of 767 clinical HSAT studies, mean signal reliability of the cut-to-fit, semi-disposable, and disposable thorax RIP belts was 83.0 ± 26.2%, 76.1 ± 24.4%, and 98.5 ± 9.3%, respectively. The signal reliability of the cannula was 92.5 ± 16.1%, 87.0 ± 23.3%, and 85.5 ± 24.5%, respectively. The automatic assessment of signal reliability for the RIP belts and cannula flow had a sensitivity of 50% and a specificity of 99% compared with manual assessment. The mean correlation of cannula flow to RIP flow from the cut-to-fit, semi-disposable, and disposable RIP belts was 0.79 ± 0.24, 0.52 ± 0.20, and 0.86 ± 0.18, respectively. CONCLUSION: The design of RIP belts affects the reliability and quality of respiratory signals. The disposable RIP belts that had integrated contacts and did not fold on top of themselves performed the best. The cut-to-fit RIP belts were most likely to be unreliable, and the semi-disposable folding belts produced the lowest-quality RIP flow signals compared to the cannula flow signal.

Power regulation and electromigration in platinum microwires.

We introduce a new experimental setup with a biasing circuit and computer control for electrical power regulation under reversing polarity in Pt microwires with dimensions of 1×10 µm(2). The circuit is computer controlled via a data acquisition board. It amplifies a control signal from the computer and drives current of alternating polarity through the sample in question. Time-to-failure investigations under DC and AC current stress are performed. We confirm that AC current stress can improve the life time of microwires at least by a factor of 10(3) compared to the corresponding time-to-failure under DC current stress.

Mechanical resistance in unstructured proteins.

Single-molecule pulling experiments on unstructured proteins linked to neurodegenerative diseases have measured rupture forces comparable to those for stable folded proteins. To investigate the structural mechanisms of this unexpected force resistance, we perform pulling simulations of the amyloid ß-peptide (Aß) and α-synuclein (αS), starting from simulated conformational ensembles for the free monomers. For both proteins, the simulations yield a set of rupture events that agree well with the experimental data. By analyzing the conformations occurring shortly before rupture in each event, we find that the mechanically resistant structures share a common architecture, with similarities to the folds adopted by Aß and αS in amyloid fibrils. The disease-linked Arctic mutation of Aß is found to increase the occurrence of highly force-resistant structures. Our study suggests that the high rupture forces observed in Aß and αS pulling experiments are caused by structures that might have a key role in amyloid formation.

Distinct phases of free α-synuclein--a Monte Carlo study.

The α-synuclein protein (αS), implicated in Parkinson's disease, shows conformational versatility. It aggregates into ß-sheet-rich fibrils, occurs in helical membrane-bound forms, is disordered as a free monomer, and has recently been suggested to have a folded helical tetramer as its main physiological form. Here, we use implicit solvent all-atom Monte Carlo methods to explore the conformational ensemble sampled by the free αS monomer. We analyze secondary structure propensities, size, and topological properties and compare with existing experimental data. Our study suggests that free αS has two distinct phases. One phase has the expected disordered character. The other phase also shows large conformational variability. However, in this phase, the ß-strand content is substantial, and the backbone fold shows statistical similarities with that in αS fibrils. Presence of this phase is consistent with data from low-temperature experiments. Conversion of disordered αS to this fibril-like form requires the crossing of a rather large apparent free-energy barrier.

Sub-wavelength bolometers: uncooled platinum wires as infrared sensors.

We present characterization results of microscopic platinum wires as bolometers. The wire lengths range from 16 µm down to 300 nm. Thus they are in many cases significantly smaller in size than the wavelength of the radiation from the 1200 K blackbody source they were exposed to. We observe a steep rise in both responsivity ℜ and detectivity D* with decreasing wire size, reaching ℜ = 3.1×10(4) V/W and D* = 2.7×10(9) cm Hz(1/2)/W at room temperature for a 300×300 nm(2) device. Two significant advantages of such small wires as bolometers are their low power requirement and fast response time. Our numerical estimations suggest response times in the order of nanoseconds for the smallest samples. They could help improve resolution and response of thermal imaging devices, for example. We believe the performance may be further improved by optimizing the design and operating parameters.