Stroke and Intracranial Hemorrhage in HeartMate II and HeartWare Left Ventricular Assist Devices: A Systematic Review.

BACKGROUND: Ischemic stroke and intracranial hemorrhage (ICH) following left ventricular assist device (LVAD) placement are major causes of morbidity. The incidence and mortality associated with these events stratified by device type have not been systematically explored. METHODS: A systematic review of PubMed was conducted from January 2007 through June 2016 for all English-language articles involving HeartMate II (HMII) and HeartWare LVAD patients. Ischemic stroke and/or ICH incidence (events per patient-year) and associated mortality rates were abstracted for each device type. RESULTS: Of 735 articles reviewed, 48 (11,310 patients) met inclusion criteria (33 HMII, six HeartWare, eight both devices, and one unspecified). The median duration of device support was 112 days (total 13,723 patient-years). Overall, ischemic stroke or ICH occurred in 9.8% (1110 persons and 0.08 events per patient year [EPPY]). Ischemic stroke occurred in a median of 6.0% or 0.06 EPPY (range 0-16% or 0-0.21 EPPY) of HMII patients versus 7.5% or 0.09 EPPY (range 4-17.1% or 0.01-0.94 EPPY) of HeartWare patients. ICH occurred in a median of 3.0% or 0.04 EPPY (range 0-13.5% or 0-0.13 EPPY) of HMII and 8.0% or 0.08 EPPY (range 3-23% or 0.01-0.56 EPPY) of HeartWare patients. The median mortality rate for LVAD-associated ischemic stroke was 31% (HMII: 33%, [range 2.4-75%] and HeartWare: 11.5% [range 3.9-40%]), and the median mortality rate following ICH was 71% (HMII: 75%, [range 3.9-100%] and HeartWare: 44%, [range 3.1-88%]). CONCLUSIONS: Ischemic stroke and ICH are common after LVAD placement, but heterogeneous event rates are reported in the literature. Given the high associated mortality, further prospective study is warranted.

Reduced Water Vapor Transmission Rate of Graphene Gas Barrier Films for Flexible Organic Field-Effect Transistors.

Preventing reactive gas species such as oxygen or water is important to ensure the stability and durability of organic electronics. Although inorganic materials have been predominantly employed as the protective layers, their poor mechanical property has hindered the practical application to flexible electronics. The densely packed hexagonal lattice of carbon atoms in graphene does not allow the transmission of small gas molecules. In addition, its outstanding mechanical flexibility and optical transmittance are expected to be useful to overcome the current mechanical limit of the inorganic materials. In this paper, we reported the measurement of the water vapor transmission rate (WVTR) through the 6-layer 10 × 10 cm(2) large-area graphene films synthesized by chemical vapor deposition (CVD). The WVTR was measured to be as low as 10(-4) g/m(2)·day initially, and stabilized at ∼0.48 g/m(2)·day, which corresponds to 7 times reduction in WVTR compared to bare polymer substrates. We also showed that the graphene-passivated organic field-effect transistors (OFETs) exhibited excellent environmental stability as well as a prolonged lifetime even after 500 bending cycles with strain of 2.3%. We expect that our results would be a good reference showing the graphene's potential as gas barriers for organic electronics.

Layer-by-layer all-transfer-based organic solar cells.

For the first time, we describe a novel cost- and time-effective vacuum-free process to fabricate bulk-heterojunction (BHJ) organic photovoltaics (OPVs) via layer-by-layer selective stamping transfer of all layers. By controlling the surface properties of polyurethane acrylate (PUA) stamping molds with ultraviolet (UV)-ozone (UVO) exposure, poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS), BHJ layer, and metal cathode were uniformly transferred layer by layer onto each of the bottom layers. Among several interfaces between each layer, we found that the interface between the active layer and metal cathode is a critical factor in obtaining conventional device-like efficiency. To enhance the interfacial connectivity between the BHJ layer and metal cathode and increase electron extraction from the BHJ layer, a titanium oxide (TiOx) interlayer was introduced. Cell performance was optimized by controlling the concentration of TiOx solution. The poly(3-hexylthiophene-2,5-diyl)/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PC60BM) BHJ device fabricated by transferring PEDOT/PSS, TiOx/active layer, and Al cathode showed 2.01% power conversion efficiency. This efficiency is not comparable to those of conventional OPVs, but our approach shows the possibility of fabricating OPVs via the layer-by-layer transfer method for the first time.

A graphene sheet exfoliated with microwave irradiation and interlinked by carbon nanotubes for high-performance transparent flexible electrodes.

High quality graphene was obtained though microwave irradiated expansion following a solution process. This method is facile, inexpensive, and produces usable results. Ultrathin, uniform graphene films were fabricated at room temperature by a vacuum filtration method. Combining carbon nanotubes (CNTs) as bridges between graphene flakes allowed the fabrication of high-performance conductive films for flexible applications, with conductivities and optical properties comparable to commercial ITO: 181 Omega sq(-1) at 82.2% transmittance after chemical treatment and doping. With future work, this versatile material could well provide an appropriate transparent electrode for flexible optical electronics.

Optical characteristics of CdSe quantum dots depending on growth conditions and surface passivation.

We investigated the effects of different growth conditions and surface passivation on the growth of CdSe quantum dots (QDs). The synthesis of CdSe QDs by pyrolysis of organometallic reagents was performed by using the hot-matrix method. In order to modify the size and quality of CdSe QDs, we controlled the growth temperature from 250 degrees C to 350 degrees C and the relative amount of trioctylphosphin (as the ligand of the Cd and Se precursors) to be injected into the coordinating solvent trioctylphosphineoxide. Moreover, an effective surface passivation of mono-disperse CdSe QDs was achieved by overcoating them with a larger band gap material, such as ZnS.