Slowing and stopping of chemical waves in a narrowing canal

The propagation of a chemical wave in a narrow, cone-shaped glass capillary was investigated. When a chemical wave propagates from the wider end to the narrower end, it slows, stops, and then disappears. A phenomenological model that considers the surface effect of the glass is proposed, and this model reproduces the experimental trends.Comment: 8 pages, 5 figure

Effects of Chain End Structures on Pyrolysis of Poly(L-lactic acid) Containing Tin Atoms

Thermal degradation of high molecular weight PLLA containing residual tin atoms was investigated as a means of controlling the reaction for feedstock recycling to L,L-lactide. To clarify the pyrolysis mechanism of the PLLA, three samples with different chain end structures were prepared, namely, as-polymerized PLLA-ap, precipitated-with-methanol PLLA-pr, and purified PLLA-H. From pyrolyzate and kinetic analyses, typical degradation mechanisms of Sn-containing PLLA were clarified. In other words, it was assumed that the pyrolysis of PLLA-ap proceeds through a zero-order weight loss process with the apparent Ea = 80-90 kJ mol-1, and with the occurrence of backbiting and transesterification reactions caused by Sn-alkoxide chain ends. The pyrolysis of PLLA-pr was also assumed to proceed via a zero-order weight loss process with apparent Ea = 120-130 kJ mol-1, with the proposed mechanism being Sn-catalyzed selective lactide elimination caused by Sn-carboxylate chain ends. Both pyrolysis of PLLA-ap and PLLA-pr produced L,L-lactide selectively. These degradation mechanisms and products are in contrast to those of PLLA-H, in which a large amount of diastereoisomers and cyclic oligomers were formed by random degradation. From this study, the complicated PLLA pyrolysis behavior as reported previously could be explained properly

Thermal degradation of poly(L-lactide): effect of alkali earth metal oxides for selective L,L-lactide formation

To achieve the feed stock recycling of poly(L-lactide) (PLLA) to L,L-lactide, PLLA composites including alkali earth metal oxides, such as calcium oxide (CaO) and magnesium oxide (MgO), were prepared and the effect of such metal oxides on the thermal degradation was investigated from the viewpoint of selective L,L-lactide formation. Metal oxides both lowered the degradation temperature range of PLLA and completely suppressed the production of oligomers other than lactides. CaO markedly lowered the degradation temperature, but caused some racemization of lactide, especially in a temperature range lower than 250 °C. Interestingly, with MgO racemization was avoided even in the lower temperature range. It is considered that the effect of MgO on the racemization is due to the lower basicity of Mg compared to Ca. At temperatures lower than 270 °C, the pyrolysis of PLLA/MgO (5 wt%) composite occurred smoothly causing unzipping depolymerization, resulting in selective L,L-lactide production. A degradation mechanism was discussed based on the results of kinetic analysis. A practical approach for the selective production of L,L-lactide from PLLA is proposed by using the PLLA/MgO composite

Effect of Sn Atom on Poly(Ｌ-lactic acid) Pyrolysis

Tin 2-ethylhexanoate is an indispensable component of commercially available poly(L-lactic acid) (PLLA). However, the thermal degradation kinetics of PLLA containing Sn have not yet clearly been established; in particular, whether the degradation mechanism is a 1st-order or a random reaction. To clarify the effects of residual Sn on PLLA pyrolysis, PLLA samples with different Sn contents from 20 to 607 ppm were prepared and subjected to pyrolysis analysed with pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS) and thermogravimetry (TG). The pyrolysis of PLLA Sn-607 (Sn content: 607 ppm) with Py-GC/MS in the temperature range of 40–400 °C selectively produced lactides. In contrast, the pyrolysis of PLLA Sn-20 (Sn content: 20 ppm) was accompanied by the production of cyclic oligomers. The dynamic pyrolysis of PLLA-Sn samples by TG clearly indicated that with an increase in Sn content there was a shift to a lower degradation temperature range and a decrease in activation energy Ea. The kinetic analysis of the dynamic pyrolysis data indicates that the Sn-catalyzed pyrolysis starts through a random degradation behaviour and then shifts to a zero-order weight loss as the main process. Three reactions were put forward as being possible mechanisms of the zero-order weight loss; one being an unzipping reaction accompanying a random transesterification, the other two being the Sn-catalyzed pseudo-selective and selective lactide elimination reactions from random positions on a polymer chain. The kinetic parameter values obtained could be adequately explained for each degradation process

Endobronchial Ultrasound-Guided Transbronchial Biopsy Using Novel Thin Bronchoscope for Diagnosis of Peripheral Pulmonary Lesions

Background:The aim of this study was to evaluate the diagnostic utility of endobronchial ultrasound (EBUS)-guided transbronchial biopsy (TBB) using a novel 3.4-mm thin bronchoscope and a 1.4-mm ultrasonic probe for peripheral pulmonary lesions.Methods:A total of 86 patients with suspected peripheral lesions were included in this prospective study. EBUS-TBBs were performed using a prototype 3.4-mm thin bronchoscope and a 1.4-mm radial ultrasonic probe under fluoroscopic guidance.Results:Twelve patients with endobronchial lesions within the segmental bronchi and three patients who did not return to follow-up were excluded from this analysis. Thus, a total of 71 patients with peripheral pulmonary lesions (mean size, 31.2 ± 12.7 mm) were included in the final analysis. The mean bronchus level reached with the thin bronchoscope was 4.6 generations. Diagnostic histologic specimens were obtained in 49 of 71 patients (69%:80% for malignant lesions and 52% for benign lesions). A definitive diagnosis of malignancy for lesions ≥20 mm and lesions <20 mm was made in 82% (31 of 38) and 67% (four of six), respectively. There were no significant complications.Conclusion:The EBUS-TBB using a 3.4-mm thin bronchoscope and a 1.4-mm radial probe is feasible, accurate, and safe for the diagnosis of peripheral pulmonary lesions

Selective Proliferation of Lactic Acid Bacteria and Accumulation of Lactic Acid during Open Fermentation of Kitchen Refuse with Intermittent pH Adjustment

When minced and autoclaved model kitchen refuse was inoculated with a small amount of non-autoclaved model kitchen refuse as seed culture, incubated at 37°C for 3-5 days and intermittently pH neutralized, 27-45 g/l of lactic acid was accumulated with a small amount of acetic acid and ethanol. The highest accumulation and highest productivity levels of lactic acid were observed at an initial and adjusted pH of 7.0 and a 6 h interval of pH adjustment. After several hours of lag, the lactic acid bacteria became the dominant cell type during the incubation, while the number of coliform bacteria and clostridia decreased. Such selective and stable accumulation of lactic acid was achieved in dozens of different experiments with various refuse preparations. In contrast, with continuous pH adjustment, Iactic acid once accumulated was labile and a small amount of butyric acid was produced, increasing the number of clostridia. The dominant bacteria isolated from the fermentation with intermittent pH adjustment were identified as Lactobacillus plantarnm and L. brevis

Chemo-Sensitive Running Droplet

Chemical control of the spontaneous motion of a reactive oil droplet moving on a glass substrate under an aqueous phase is reported. Experimental results show that the self-motion of an oil droplet is confined on an acid-treated glass surface. The transient behavior of oil-droplet motion is also observed with a high-speed video camera. A mathematical model that incorporates the effect of the glass surface charge is built based on the experimental observation of oil-droplet motion. A numerical simulation of this mathematical model reproduced the essential features concerning confinement within a certain chemical territory of oil-droplet motion, and also its transient behavior. Our results may shed light on physical aspects of reactive spreading and a chemotaxis in living things.Comment: 17 pages, 10 figure

Regulation of Id2 expression by CCAAT/enhancer binding protein β

Mice deficient for Id2, a negative regulator of basic helix–loop–helix (bHLH) transcription factors, exhibit a defect in lactation due to impaired lobuloalveolar development during pregnancy, similar to the mice lacking the CCAAT enhancer binding protein (C/EBP) β. Here, we show that Id2 is a direct target of C/EBPβ. Translocation of C/EBPβ into the nucleus, which was achieved by using a system utilizing the fusion protein between C/EBPβ and the ligand-binding domain of the human estrogen receptor (C/EBPβ-ERT), demonstrated the rapid induction of endogenous Id2 expression. In reporter assays, transactivation of the Id2 promoter by C/EBPβ was observed and, among three potential C/EBPβ binding sites found in the 2.3 kb Id2 promoter region, the most proximal element was responsible for the transactivation. Electrophoretic mobility shift assay (EMSA) identified this element as a core sequence to which C/EBPβ binds. Chromatin immunoprecipitation (ChIP) furthermore confirmed the presence of C/EBPβ in the Id2 promoter region. Northern blotting showed that Id2 expression in C/EBPβ-deficient mammary glands was reduced at 10 days post coitus (d.p.c.), compared with that in wild-type mammary glands. Thus, our data demonstrate that Id2 is a direct target of C/EBPβ and provide insight into molecular mechanisms underlying mammary gland development during pregnancy