Litter carbon dynamics analysis in forests in an arid ecosystem with a model incorporating the physical removal of litter

金沢大学理工研究域自然システム学系Arid land afforestation could be a countermeasure for global warming, and a project for developing and evaluating techniques for arid land afforestation and reforestation has been carried out in Sturt Meadows near Leonora, Western Australia. As a part of this project, the litter carbon dynamics were investigated at three Acacia aneura forest sites, using a litter carbon model incorporating the physical removal of litter by winds, floods, etc. Based on the field observation data of above ground plant biomass, annual litter fall, existing amount of the litter, and also litter decomposition rate constants separately obtained for leaf litter and woody litter, we investigated the carbon flows at these forest sites, especially the annual amount of litter physically removed from the sites by floods or winds. As a result, it is estimated that annual physical removal of litter amounted to 59-75% of the annual litter fall, and the litter removal rate constants were from 0.38 to 0.55 year-1. Roughly one third to a half of the existing litter is removed annually from the sites. There was also a tendency that as the canopy coverage decreases, the litter removal rate constant increases. For this type of ecosystem, which is susceptible to the run-off of water and strong winds, we consider the taking into account of the physical removal of the litter is essential for analyzing the carbon dynamics in the ecosystem. © 2008 Elsevier B.V. All rights reserved

Effect of Different Direct Compaction Grades of Mannitol on the Storage Stability of Tablet Properties Investigated Using a Kohonen Self-Organizing Map and Elastic Net Regression Model

This study tested 15 direct compaction grades to identify the contribution of different grades of mannitol to the storage stability of the resulting tablets. After preparing the model tablets with different values of hardness, they were stored at 25 °C, 75% relative humidity for 1 week. Then, measurement of the tablet properties was conducted on both pre- and post-storage tablets. The tablet properties were tensile strength (TS), friability, and disintegration time (DT). The experimental data were analyzed using a Kohonen self-organizing map (SOM). The SOM analysis successfully classified the test grades into three distinct clusters having different changes in the behavior of the tablet properties accompanying storage. Cluster 1 showed an obvious rise in DT induced by storage, while cluster 3 showed a substantial change in mechanical strength of the tablet including a reduction in the TS and a rise in friability. Furthermore, the data were analyzed using an Elastic net regression technique to investigate the general relationships between the powder properties of mannitol and the change behavior of the tablet properties. Consequently, we succeeded in identifying the crucial powder properties for the storage stability of the resulting tablets. This study provides advanced technical knowledge to characterize the effect of different direct compaction grades of mannitol on the storage stability of tablet properties

A Time-Domain NMR Study of the State of Water in Wet Granules with Different Fillers and Its Contribution to the Wet Granulation Process and to the Characteristics of Granules

The different states of water incorporated in wet granules were studied by a low-field benchtop 1H-NMR time-domain NMR (TD-NMR) instrument. Wet granules consisting different fillers [cornstarch (CS), microcrystalline cellulose (MCC), and D-mannitol (MAN)] with different water contents were prepared using a high-speed granulator, and then their spin–spin relaxation time (T2) was measured using the NMR relaxation technique. The experimental T2 relaxation curves were analyzed by the two-component curve fitting, and then the individual T2 relaxation behaviors of solid and water in wet granules were identified. According to the observed T2 values, it was confirmed that the molecular mobility of water in CS and MCC granules was more restricted than that in the MAN granule. The state of water appeared to be associated with the drying efficiency and moisture absorption capacity of wet granules. Thus, it was confirmed that the state of water significantly affected the wet granulation process and the characteristics of the resultant granules. In the final phase of this study, the effects of binders on the molecular mobility of water in granulation fluids and wet granules were examined. The state of water in granulation fluids was substantially changed by changing the binders. The difference was still detected in wet granules prepared by addition of these fluids to the fillers. In conclusion, TD-NMR can offer valuable knowledge on wet granulation from the viewpoint of molecular mobility of water. © 2019 The Pharmaceutical Society of Japan

Modeling of quantitative relationships between physicochemical properties of active pharmaceutical ingredients and tensile strength of tablets using a boosted tree

<p><b>Objectives:</b> The aim of this study was to explore the potential of boosted tree (BT) to develop a correlation model between active pharmaceutical ingredient (API) characteristics and a tensile strength (TS) of tablets as critical quality attributes.</p> <p><b>Methods:</b> First, we evaluated 81 kinds of API characteristics, such as particle size distribution, bulk density, tapped density, Hausner ratio, moisture content, elastic recovery, molecular weight, and partition coefficient. Next, we prepared tablets containing 50% API, 49% microcrystalline cellulose, and 1% magnesium stearate using direct compression at 6, 8, and 10 kN, and measured TS. Then, we applied BT to our dataset to develop a correlation model. Finally, the constructed BT model was validated using <i>k</i>-fold cross-validation.</p> <p><b>Results:</b> Results showed that the BT model achieved high-performance statistics, whereas multiple regression analysis resulted in poor estimations. Sensitivity analysis of the BT model revealed that diameter of powder particles at the 10th percentile of the cumulative percentage size distribution was the most crucial factor for TS. In addition, the influences of moisture content, partition coefficients, and modal diameter were appreciably meaningful factors.</p> <p><b>Conclusions:</b> This study demonstrates that BT model could provide comprehensive understanding of the latent structure underlying APIs and TS of tablets.</p