A Low-Cost, Portable, High-Throughput Wireless Sensor System for Phonocardiography Applications

This paper presents the design and testing of a wireless sensor system developed using a Microchip PICDEM developer kit to acquire and monitor human heart sounds for phonocardiography applications. This system can serve as a cost-effective option to the recent developments in wireless phonocardiography sensors that have primarily focused on Bluetooth technology. This wireless sensor system has been designed and developed in-house using off-the-shelf components and open source software for remote and mobile applications. The small form factor (3.75 cm ´ 5 cm ´ 1 cm), high throughput (6,000 Hz data streaming rate), and low cost ($13 per unit for a 1,000 unit batch) of this wireless sensor system make it particularly attractive for phonocardiography and other sensing applications. The experimental results of sensor signal analysis using several signal characterization techniques suggest that this wireless sensor system can capture both fundamental heart sounds (S1 and S2), and is also capable of capturing abnormal heart sounds (S3 and S4) and heart murmurs without aliasing. The results of a denoising application using Wavelet Transform show that the undesirable noises of sensor signals in the surrounding environment can be reduced dramatically. The exercising experiment results also show that this proposed wireless PCG system can capture heart sounds over different heart conditions simulated by varying heart rates of six subjects over a range of 60–180 Hz through exercise testing

Controlled Ring-Opening Metathesis Polymerization with Polyisobutylene-Bound Pyridine-Ligated Ru(II) Catalysts

This study describes the use of polyisobutylene (PIB) to phase-anchor pyridine ligands that form a phase-separable Grubbs third-generation catalyst. We further show that this complex is useful in ring-opening metathesis polymerization (ROMP) reactions. These PIB-bound pyridine-ligated Grubbs catalysts provide the same benefits of control over polymer chain growth and polydispersity of the product as their low-molecular-weight analogs and reduce Ru leaching in ROMP products from approximately 16% (820 ppm residues) as seen with a similar pyridine-ligated catalyst to a value of approximately 3% (160 ppm residues). These labile ligands are shown to be as effective at generating separable metal complexes as less labile PIB-functionalized N-heterocyclic carbene catalyst ligands that are typically used for immobilization but that require a multistep synthesis

Recoverable Reusable Polyisobutylene (PIB)-Bound Ruthenium Bipyridine (Ru(PIB-bpy)₃Cl₂) Photoredox Polymerization Catalysts

Polyisobutylene (PIB)-bound ruthenium bipyridine [Ru­(PIB-bpy)₃]²⁺ metal complexes were prepared from PIB ligands formed by alkylation of 4,4′-dimethylbipyridine with polyisobutylene bromide. The product Ru­(PIB-bpy)₃Cl₂ complexes with at least one PIB ligand per bipyridine unit function as soluble recyclable photoredox catalysts in free radical polymerization of acrylate monomers under visible light irradiation at 25 °C with ethyl 2-bromoisobutyrate as the initiator in the presence of diisopropylethylamine. The polyacrylate products contained only about 1 ppm Ru contamination. This PIB-bound catalyst was recyclable and showed about 50-fold less Ru leaching as compared to Ru leaching in a polymerization catalyzed by the low molecular weight Ru catalyst, Ru­(bpy)₃(PF₆)₂

Polyethylene as a Cosolvent and Catalyst Support in Ring-Opening Metathesis Polymerization

Polyethylene oligomers (PE_Olig) can be used as cosolvents and sometimes soluble catalyst supports in ring-opening metathesis polymerization (ROMP) reactions. As a catalyst support, this polyolefin serves as an <i>N</i>-heterocyclic carbene ligand for a ROMP catalyst, making it soluble at 70 °C and insoluble at room temperature. As a cosolvent, unfunctionalized PE oligomers facilitate quantitative separation of PE_Olig-bound Ru-catalyst residues from polymer products. In these cases, the insolubility of the unfunctionalized polyethylene (Polywax) and its entrapment of the PE_Olig-supported Ru residue in the product phase at room temperature afford ROMP products with Ru contamination lower than other procedures that use soluble catalysts. These separations require only physical processes to separate the product and catalyst residuesno additional solvents are necessary. Control experiments suggest that most (ca. 90%) of the Ru leaching that is seen results from Ru byproducts formed in the vinyl ether quenching step and not from the polymerization processes involving the PE_Olig-supported Ru complex