Control of free-radical emulsion polymerization of methyl methacrylate by oxygen injection. II. Experimental study

Oxygen injection has been proposed and experimentally demonstrated as an effective control measure for limiting the rate of heat release and altering the rate of polymerization in emulsion processes. A detailed mathematical model has been previously developed to describe the system behavior with and without oxygen injection. A simple lab scale apparatus was constructed and run extensively. Only trace quantities of oxygen are needed to inhibit the reaction completely. The facile response makes this method attractive for fast temperature control. However, because of the rapid penetration of dissolved oxygen into the polymer particles, growing radical chains are terminated prematurely, lowering product molecular weights. To minimize this detrimental effect, pulsed oxygen control is used and extensive experimental work was performed to determine the effects of controller set points on molecular weight. Moderate oxygen flows and moderate set point temperatures are found to give the optimal response without significant lowering of the final molecular weight. Injected quantities agree well with the order-of-magnitude sparging calculations needed to completely stop initiation. However, complete agreement between model simulations and experimental results was not reached due to an unmeasured loss of monomer from the reactor. Chain transfer to monomer is found to be important in modeling the polymer molecular weight. It has, however, a negligible effect on the reaction rate.     

Giant cell tumor of lumbar vertebra. A case report with 13-year followup

A combined one stage anterior and posterior approach was used to excise a giant cell tumor involving the second lumbar vertebra. The tumor involved the anterior and posterior elements of the vertebra. A wide excision was feasible with immediate stabilization using the Luque instrumentation posteriorly and fibular strut grafts supporting the vertebral bodies anteriorly. The followup period was 13 years. There is no recurrence, and the patient has no symptoms of disease, and the fibular grafts are fully incorporated.     

Fitting a hand-glove prosthesis to enhance the reconstructed mutilated hand

We report a unique case of tubular polyclonal immunoglobulin G (IgG) deposition disease (PIDD) superimposed on diabetic nephropathy in an 84-year-old man presenting with subacute renal failure and proteinuria. The deposits were located exclusively between the tubular epithelial cells and the tubular basement membranes (TBMs) and stained intensely with antisera to IgG heavy chain and both kappa and lambda light chains. Electron microscopy revealed large predominantly extracellular electron-dense deposits with a distinctive curvilinear substructure. The associated light microscopic findings of tubular simplification with features of acute tubular necrosis implicate this tubulopathy as the cause of the acute renal failure. This appears to represent a unique entity that does not fit into any previously described category of renal tubular immune complex or immunoglobulin deposition disease.     

Indium and tin oxide nanowires by vapor-liquid-solid growth technique

Regular three-dimensional (3-D) arrays of crystalline SnO₂-In₂O₃ nanowires were produced on m-sapphire using a gold catalyst-assisted vapor-liquid-solid growth process. The growth characteristics at multiple growth conditions were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray photoemission spectroscopy (XPS), and Rutherford backscattering spectroscopy (RBS) to evaluate the functional dependence of nanowire structure and composition on growth parameters such as temperature and source composition. The results indicate that nanowires of mixed composition are not possible from the catalytic clusters; rather, a mixture of indium and tin oxide wires are formed in the range of conditions investigated here.     

Information Theoretic Weighted Fuzzy Clustering Ensemble

In order to improve performance and robustness of clustering, it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique. Fuzzy clustering ensemble approaches attempt to improve the performance of fuzzy clustering tasks. However, in these approaches, cluster (or clustering) reliability has not paid much attention to. Ignoring cluster (or clustering) reliability makes these approaches weak in dealing with low-quality base clustering methods. In this paper, we have utilized cluster unreliability estimation and local weighting strategy to propose a new fuzzy clustering ensemble method which has introduced Reliability Based weighted co-association matrix Fuzzy C-Means (RBFCM), Reliability Based Graph Partitioning (RBGP) and Reliability Based Hyper Clustering (RBHC) as three new fuzzy clustering consensus functions. Our fuzzy clustering ensemble approach works based on fuzzy cluster unreliability estimation. Cluster unreliability is estimated according to an entropic criterion using the cluster labels in the entire ensemble. To do so, the new metric is defined to estimate the fuzzy cluster unreliability; then, the reliability value of any cluster is determined using a Reliability Driven Cluster Indicator (RDCI). The time complexities of RBHC and RBGP are linearly proportional with the number of data objects. Performance and robustness of the proposed method are experimentally evaluated for some benchmark datasets. The experimental results demonstrate efficiency and suitability of the proposed method.     

Customized staple fixation in hand and wrist surgery

Fixation of small bones in the adult and the child's hands remains a challenge. The authors present a technique of bone fixation using customized staples made intraoperatively from K-wires (0.9-1.6 mm in diameter). Their specific purpose was to provide axial alignment and rotational stability for carpal bone fixation and for epiphysiodesis in phalanges. This technique was used in 14 cases (11 adult and three paediatric). No bone shattering, implant breakage, implant loosening or infection occurred. As K-wires are quite malleable, custom sized and shaped staples which follow the bone contours could be made to give a more exact fixation. All cases had satisfactory outcomes, achieving the preoperative objectives of bony fixation. This method is safe, precise and technically easy. It is also relatively cheap and only requires simple, standard instruments.     

Quinacridone‐Based Electron Transport Layers for Enhanced Performance in Bulk‐Heterojunction Solar Cells

A water/alcohol‐soluble small molecule based on the commercially available pigment quinacridone is employed as an electron transport layer in organic photovoltaics. The quinacridone derivative is utilized in solution‐processed bulk‐heterojunction solar cells to improve primarily the fill factor of the devices, contributing to an upwards of 19% enhancement in the power conversion efficiency relative to the control devices with no electron transport layer. The facile synthesis of the quinacridone derivative coupled with the ease of device fabrication via solution processing provide a simple, yet effective means of improving the performance of existing organic photovoltaic cells.     

The Effect of DREADD Activation of Leptin Receptor Positive Neurons in the Nucleus of the Solitary Tract on Sleep Disordered Breathing

Obstructive sleep apnea (OSA) is recurrent obstruction of the upper airway due to the loss of upper airway muscle tone during sleep. OSA is highly prevalent, especially in obesity. There is no pharmacotherapy for OSA. Previous studies have demonstrated the role of leptin, an adipose-tissue-produced hormone, as a potent respiratory stimulant. Leptin signaling via a long functional isoform of leptin receptor, LEPR^b, in the nucleus of the solitary tract (NTS), has been implicated in control of breathing. We hypothesized that leptin acts on LEPR^b positive neurons in the NTS to increase ventilation and maintain upper airway patency during sleep in obese mice. We expressed designer receptors exclusively activated by designer drugs (DREADD) selectively in the LEPR^b positive neurons of the NTS of Lepr^b-Cre-GFP mice with diet-induced obesity (DIO) and examined the effect of DREADD ligand, J60, on tongue muscle activity and breathing during sleep. J60 was a potent activator of LEPR^b positive NTS neurons, but did not stimulate breathing or upper airway muscles during NREM and REM sleep. We conclude that, in DIO mice, the stimulating effects of leptin on breathing during sleep are independent of LEPR^b signaling in the NTS.     

Synthesis of Densely Immobilized Gold-Assembled Silica Nanostructures

In this study, dense gold-assembled SiO₂ nanostructure (SiO₂@Au) was successfully developed using the Au seed-mediated growth. First, SiO₂ (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO₂ surface. Then, Au NPs were grown on the prepared SiO₂@Au seed by reducing chloroauric acid (HAuCl₄₎ by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO₂ surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO₂@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO₂@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH₃), and a better peroxidase-like catalysis activity for 5,5′-Tetramethylbenzidine (TMB) and hydrogen peroxide (H₂O₂) reaction. The catalytic activity of SiO₂@Au was two times better than that of HF-treated SiO₂@Au. When SiO₂@Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO₂@Au was also stronger than that of HF-treated SiO₂@Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.