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

Pyrolysis Kinetics of Poly(L-lactide) with Carboxyl and Calcium Salt End Structures

To clarify the pyrolysis mechanism of poly(L-lactide), which has been reported as complex, the thermal decomposition of carboxyl type and calcium ion end capped PLLA (PLLA-H and PLLA-Ca, respectively) was investigated by means of thermogravimetric analysis (TG), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The TG data revealed that PLLA-Ca has a lower pyrolysis temperature (220~360°C) than that of carboxyl type PLLA-H (280~370°C). The apparent activation energy of the decomposition reaction was estimated from TG curves at different heating rates by plural methods to be 176 and 98 kJ mol-1 for PLLA-H and PLLA-Ca, respectively. Further kinetic studies indicated that PLLA-H degraded mainly through a random reaction with a pre-exponential factor A=2.0×1012 s-1, whereas PLLA-Ca degraded by way of a 1st-order reaction with A=8.4×105 s-1. Pyrolysis products of PLLA-H were composed of lactides and other cyclic oligomers, while the degradation products of PLLA-Ca were principally lactides. The main reaction pathway for PLLA-H pyrolysis was regarded as the random transesterification, whereas for PLLA-Ca pyrolysis the unzipping depolymerization process was dominant

Continuous oxygen saturation and risk of retinopathy of prematurity in a Japanese cohort

Kubota H., Fukushima Y., Kawasaki R., et al. Continuous oxygen saturation and risk of retinopathy of prematurity in a Japanese cohort. British Journal of Ophthalmology , bjo-2023-324225 (2024); https://doi.org/10.1136/bjo-2023-324225.Background/aims : We assessed the associations between retinopathy of prematurity (ROP) and continuous measurements of oxygen saturation (SpO2), and developed a risk prediction model for severe ROP using birth data and SpO2 data. Methods : This retrospective study included infants who were born before 30 weeks of gestation between August 2009 and January 2019 and who were screened for ROP at a single hospital in Japan. We extracted data on birth weight (BW), birth length, gestational age (GA) and minute-by-minute SpO2 during the first 20 days from the medical records. We defined four SpO2 variables using sequential measurements. Multivariate logistic regression was used to develop a model that combined birth data and SpO2 data to predict treatment-requiring ROP (TR-ROP). The model’s performance was evaluated using the area under the receiver operating characteristic curve (AUC). Results : Among 350 infants, 83 (23.7%) required ROP treatment. The SpO2 variables in infants with TR-ROP differed significantly from those with non-TR-ROP. The average SpO2 and high SpO2 showed strong associations with GA (r=0.73 and r=0.70, respectively). The model incorporating birth data and the four SpO2 variables demonstrated good discriminative ability (AUC=0.83), but it did not outperform the model incorporating BW and GA (AUC=0.82). Conclusion Data obtained by continuous SpO2 monitoring demonstrated valuable associations with severe ROP, as well as with GA. Differences in the distribution of average SpO2 and high SpO2 between infants with TR-ROP and non-TR-ROP could be used to establish efficient cut-off values for risk determination

First molecular and isotopic evidence of millet processing in prehistoric pottery vessels

Analysis of organic residues in pottery vessels has been successful in detecting a range of animal and plant products as indicators of food preparation and consumption in the past. However, the identification of plant remains, especially grain crops in pottery, has proved elusive. Extending the spectrum is highly desirable, not only to strengthen our understanding of the dispersal of crops from centres of domestication but also to determine modes of food processing, artefact function and the culinary significance of the crop. Here, we propose a new approach to identify millet in pottery vessels, a crop that spread throughout much of Eurasia during prehistory following its domestication, most likely in northern China. We report the successful identification of miliacin (olean-18-en-3β-ol methyl ether), a pentacyclic triterpene methyl ether that is enriched in grains of common/broomcorn millet (Panicum miliaceum), in Bronze Age pottery vessels from the Korean Peninsula and northern Europe. The presence of millet is supported by enriched carbon stable isotope values of bulk charred organic matter sampled from pottery vessel surfaces and extracted n-alkanoic acids, consistent with a C4 plant origin. These data represent the first identification of millet in archaeological ceramic vessels, providing a means to track the introduction, spread and consumption of this important crop

Ancient lipids document continuity in the use of early hunter-gatherer pottery through 9,000 years of Japanese prehistory

The earliest pots in the world are from East Asia and date to the Late Pleistocene. However, ceramic vessels were only produced in large numbers during the warmer and more stable climatic conditions of the Holocene. It has long been assumed that the expansion of pottery was linked with increased sedentism and exploitation of new resources that became available with the ameliorated climate, but this hypothesis has never been tested. Through chemical analysis of their contents, we herein investigate the use of pottery across an exceptionally long 9,000-y sequence from the Jōmon site of Torihama inwestern Japan, intermittently occupied from the Late Pleistocene to the mid-Holocene. Molecular and isotopic analyses of lipids from 143 vessels provides clear evidence that pottery across this sequence was predominantly used for cooking marine and freshwater resources, with evidence for diversification in the range of aquatic products processed during the Holocene. Conversely, there is little indication that ruminant animals or plants were processed in pottery, although it is evident from the faunal and macrobotanical remains that these foods were heavily exploited. Supported by other residue analysis data from Japan, our results show that the link between pottery and fishing was established in the Late Paleolithic and lasted well into the Holocene, despite environmental and socio-economic change. Cooking aquatic products in pottery represents an enduring social aspect of East Asian hunter-gatherers, a tradition based on a dependable technology for exploiting a sustainable resource in an uncertain and changing world

Dram1 regulates DNA damage-induced alternative autophagy

Autophagy is an evolutionarily conserved process that degrades subcellular constituents. Mammalian cells undergo two types of autophagy; Atg5-dependent conventional autophagy and Atg5-independent alternative autophagy, and the molecules required for the latter type of autophagy are largely unknown. In this study, we analyzed the molecular mechanisms of genotoxic stress-induced alternative autophagy, and identified the essential role of p53 and damage-regulated autophagy modulator (Dram1). Dram1 was sufficient to induce alternative autophagy. In the mechanism of alternative autophagy, Dram1 functions in the closure of isolation membranes downstream of p53. These findings indicate that Dram1 plays a pivotal role in genotoxic stress-induced alternative autophagy