A visual feedback system for micromanipulation with stereoscopic microscope

A stereoscopic microscope is widely used in a micromanipulation such as to operate genes and to inspect integration circuits. As in these tasks the micromanipulation is handled and makes too heavy burden to operators, it is desirable to perform the micromanipulation automatically. In this paper, we propose a visual feedback system for micromanipulation with stereoscopic microscope. This system takes less time to control the manipulator by reducing searching area to detect an object </p

Thermal Stability of Poly (L-lactide): Influence of End Protection by Acetyl Group

Thermal stability of end-protected poly (L-lactide) (PLLA) was studied by dynamic thermal degradation and pyrolyzate analyses. The treatment of PLLA by acetic anhydride resulted in the acetylation of end hydroxyl groups, and at the same time a decrease in the residual Sn content in the polymer. The thermal degradation of the acetylated PLLA-Ac showed a shift to a 40-50°C higher degradation temperature range than that of untreated, high Sn content PLLA, but exhibited nearly the same degradation behavior as the untreated PLLA with a comparable Sn content. Purified metal-free PLLA-H showed good thermal stability, having the highest degradation temperature range. Interestingly, despite the end-protection, the acetylated metal-free PLLA-H/Ac decomposed at almost the same temperature as that of PLLA-H. From pyrolyzate and kinetic analyses, it was found that the contribution of the hydroxyl-end acetylation to the stability of PLLA was negligible, except for the stabilization effect due to the elimination of residual Sn during the acetylation process

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

Fluorescence imaging in vivo visualizes delayed gastric emptying of liquid enteral nutrition containing pectin

BACKGROUND: Semi-solidification by gelation or increased viscosity could slow the influx of liquid enteral nutrition (EN) into the small intestine. A liquid EN formula containing pectin that gels under acidic conditions such as those found in the stomach has been developed. A new near-infrared fluorescent imaging reagent was used to non-invasively acquire real time images of gastric emptying in a murine model in vivo. We postulated that the EN formula delays gastric emptying and tested this hypothesis using imaging in vivo. METHODS: Male BALB/c mice were given an oral bolus injection of a liquid EN containing the fluorescence reagent GastroSense750 with or without pectin. The EN in the stomach was visualized in vivo at various intervals using a non-invasive live imaging system and fluorescent signals were monitored from the stomach, which was removed at 60 min after EN ingestion. RESULTS: The fluorescence intensity of signals in stomachs in vivo and in resected stomachs was lower and attenuated over time in mice given EN without, than with pectin. CONCLUSIONS: Adding a gelling agent such as pectin delayed the transit of liquid EN from the stomach. Fluorescence imaging can visualize the delayed gastric emptying of EN containing pectin

Racemization on Thermal Degradation of Poly(L-lactide) with Calcium Salt End Structure

Poly(L-lactide) with calcium salt end structure (PLLA-Ca) is a promising material for PLLA recycling because of the ease of lactide recovery through the unzipping depolymerization process. However, the pyrolysis of PLLA-Ca also causes meso-lactide to form. In this article, the racemization in PLLA-Ca pyrolysis was analyzed in detail with Py-MS, Py-GC/MS, and a glass tube oven. The results suggested that at a temperature lower than 250°C, nucleophilic attack by a carboxylate anion end on an asymmetrical methyne carbon in a penultimate lactate unit occurred, resulting in the predominant formation of meso-lactide. On the other hand, also at temperatures over 320°C, by-reactions, such as enolization reactions, caused the meso-lactide to form, but not dominantly. In the temperature range of 250-320°C, L,L-lactide was produced exclusively, because unzipping depolymerization proceeded as the main reaction. This is a very significant result for PLLA recycling, because PLLA-Ca is an easily recyclable material, which depolymerizes based on the 1st-order weight loss process

Simple Procedure for Polystyrene-based Nanocomposite Preparation by Vapor-Phase Assisted Surface Polymerization

Polystyrene (PSt)-based copolymer/montmorillonite (MMT) nanocomposites were prepared by an in-situ vapor-phase assisted surface polymerization (VASP) as a solventless method using an organically modified MMT and a free radical initiator. Simultaneous and consecutive VASP of styrene (St) and methyl methacrylate (MMA) on the pre-modified MMT induced the accumulation of poly(MMA-ran-St) and poly(MMA-block-St) on the MMT surface, resulting in effective intercalation and exfoliation of silicate layers. The homogeneously dispersed silicate platelets in the polymer matrices were confirmed by X-ray diffraction and transmission electron microscope analyses. An important contributor to this phenomenon must be the particular interaction between a small amount of MMA-units and silicate surfaces. This approach allows the nanocomposites with accompanying intercalation and exfoliation of silicate layers to be applied to a wide range of vaporizable monomers which in the absence of this technique would be otherwise difficult to individually prepare

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

Thermal Degradation Behavior of Poly (lactic acid) Stereocomplex

Thermal degradation of poly(lactic acid) stereocomplex (scPLA) was investigated to clarify the pyrolysis mechanism. Three scPLA samples with different chain end structures were prepared, namely, as-polymerized scPLA-ap, precipitated-with-methanol scPLA-pr, and purified metal-free scPLA-H. From the analyses of thermal degradation kinetics and pyrolyzates of the scPLA samples, typical degradation mechanisms of these scPLAs were proposed as follows: The pyrolysis of scPLA-ap proceeds through main unzipping depolymerization caused by Sn-alkoxide chain ends with apparent Ea = 80-100kJ mol-1, showing zero-order weight loss behavior. The pyrolysis of scPLA-pr also proceeds via a zero-order weight loss process consisting of main Sn-catalyzed selective lactide elimination with apparent Ea = 100-120kJ mol-1 caused by Sn-carboxylate chain ends. The pyrolyzates from scPLA-ap and scPLA–pr were predominantly L,L-/D,D-lactides. In the case of scPLA-H, random degradation is a main process, producing a large amount of meso-lactide and cyclic oligomers. These degradation mechanisms were nearly the same as those of the corresponding PLLAs, except that the scPLA-ap pyrolysis started at higher temperature due to the higher melting point of scPLA

Thermal Degradation Behavior of Poly(Lactic Acid) in a Blend with Polyethylene

Poly(L-lactic acid) (PLLA) is a candidate for feedstock recycling materials, because it easily depolymerizes back into the cyclic monomer, L,L-lactide. To examine the recycling of PLLA from blends with other kinds of polymers, a polymer blend of PLLA and linear low-density polyethylene (LLDPE) was prepared and thermally degraded with a degradation catalyst: magnesium oxide (MgO) in a thermogravimeter/differential thermal analyzer (TG/DTA) and pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS). To clarify the influence of the LLDPE ingredient in the blend, the thermal degradation data were analyzed kinetically using two simulation methods: integration and random degradation analytical methods. From the results, it was found that PLLA was effectively depolymerized in the presence of MgO into L,L-lactide with a low racemization ratio and that LLDPE had no effect on the feedstock recycling of PLLA