Polyhydroxyalkanoate (PHA) and poly(propylene carbonate) (PPC) are blended in order to investigate their mutual contributions in terms of functional properties. A wide range of blend composition is processed through extrusion from dry blends. Droplet‐matrix morphology is observed for all samples. Thermal investigations reveal the PPC effect on the PHA crystallization process with a decrease and broadening of the crystallization temperature window and on the depression of its glass transition temperature. This investigation also confirms the as yet un‐reported non‐miscibility of this kind of blend. However, a slight phase interaction is expected since thermal behavior of PHA is impacted. The fragile behavior of PHA is balanced by the high ductility of PPC. The weak strain at break of PHA can thus be increased by up to 200% although a significant amount of PPC is needed to start modifying this property. Stress at break and modulus are linearly decreased from pure PHA to pure PPC values. PPC also acts as an impact modifier for PHA. In terms of barrier properties, PHA brings a large contribution even at low content to the initially high oxygen and water vapor permeability of PPC.
Biomonitoring of workers was carried out in three working areas--an artificial target factory, an aluminum plant, and an electrometallurgy plant--to assess exposure to PAHs. All the 48 hr-voided urine samples of the exposed workers were collected and the 3-hydroxybenzo[ a ]pyrene (3-OHB a P) and 1-hydroxypyrene (1-OHPy) analyzed according to procedures using automated column-switching high-performance liquid chromatography. The exposure profiles indicate an important lag between the excretion of the two metabolites: the maximum of 3-OHB a P urinary excretion is observed 10 to 17 hr after the 1-OHPy maximum, with a much closer correlation ( r = 0.81) than that obtained with both metabolites in real time ( r = 0.21). This delayed excretion agrees with data from animal intoxication studies (intravenous administration or inhalation). Mean ratios of 1-OHPy to 3-OHB a P were studied without lag (varying from 2,230 to 15,330) and with a lag of 16 hr (varying from 940 to 8,390). 相似文献
Stop dividing : In the quest for antitumorigenic compounds, aurora A kinase has recently emerged as a potential drug target. In this paper three novel aurora inhibitors (shown in the illustration) have been tested for their biological activity in cultured cells. One of them (TC‐28) appears to be a promising specific aurora A inhibitor in vivo.
The Na+/I? symporter (NIS) mediates iodide uptake in the thyroid gland as well as in other NIS‐expressing cells. This transport is the basis for an emerging approach to selective cancer cell destruction by using radioiodide after targeted NIS gene transfer. Therapeutic efficacy requires that radioiodide retention be maximized in tumor cells. A first generation of forty imidazo[2,1‐b]thiazole derivatives as iodide efflux inhibitors is described along with the evaluation of their biological properties. Structure–activity relationship studies by using radioiodide uptake in rat thyroid‐derived cells (FRTL5) revealed that the 5,6‐dihydroimidazo[2,1‐b]thiazole heterocycle is required for activity. Introduction of electron‐donor substituents on the 3‐biphenyl moiety led to the discovery of novel potent compounds. A compound was identified with enhanced potency compared to reference 1 . These molecules give the possibility to increase the cellular retention of radioiodide in NIS‐expressing tumors, leading to higher absorbed doses and killing efficacy.相似文献
The present study is aimed to investigate the effect of multiple extrusions of iPP/WF composites with and without EBAGMA used as compatibilizer. The degradation induced by the recycling processes was evaluated through changes in molecular structure, morphology, rheology, thermal and mechanical properties. The results showed that after six cycles, the presence of WF imparts stability to the composite materials. This effect was enhanced for the compatibilized samples. Further, SEM revealed better dispersion of the WF in the matrix. In contrast, it was confirmed that after the first recycling, both the molecular weight and the properties of PP drastically decreased due to chain scission resulting from degradation.
Silver nanoparticles (AgNPs) are used in the agri‐food sector, which can lead to their ingestion. Their interaction with food and their passage through the gastrointestinal tract can alter their properties and influence their fate upon ingestion. Therefore, this study aims at developing an in vitro method to follow the fate of AgNPs in the gastrointestinal tract. After incorporation of AgNPs into a standardized food matrix, a precolonic digestion is simulated and AgNPs are characterized by different techniques. The presence of food influences the AgNPs properties by forming a corona around nanoparticles. Even if the salivary step does not impact significantly the AgNPs, the pH decrease and the digestive enzymes induce the agglomeration of AgNPs during the gastric phase, while the addition of intestinal fluids disintegrates these clusters. AgNPs can thus reach the intestinal cells under nanometric form, although the presence of food and gastrointestinal fluids modifies their properties compared to pristine AgNPs. They can form a corona around the nanoparticles and act as colloidal stabilizer, which can impact the interaction of AgNPs with intestinal epithelium. This study demonstrates the importance of taking the fate of AgNPs in the gastrointestinal tract into account to perform an accurate risk assessment of nanomaterials. 相似文献
This work presents a new ultrasonic fatigue testing device for studying the initiation and propagation mechanisms of internal microstructurally short fatigue cracks using in situ synchrotron tomography. Its principle is described as well as the method used for automatically detecting crack initiation and its subsequent growth. To promote internal crack initiation, specimens containing internal casting defects were tested between the high cycle and very high cycle fatigue regimes (107‐109 cycles). Preliminary results show the ability of this new device to initiate an internal microstructurally short crack in a reasonable testing time and monitor its growth. 相似文献
Nowadays, due to the increasing complexity of business environment, especially demand uncertainty, supply chain managers need to establish more-effective sourcing and distribution strategies to ensure high customer service and low stock costs. To overcome this challenge multi-echelon network structures and alternative distribution strategies such as lateral transshipments and multiple sourcing should be considered in inventory optimisation models. In this article, we propose a scenario-based modelling approach to solve a two-stage multi-echelon inventory optimisation problem with a non-stationary demand. The model is based on a distribution requirements planning (DRP) approach and minimises the expected total cost that is composed of the fixed allocation, inventory holding, procurement, transportation, and back-ordering costs. Alternative inventory optimisation models, including the lateral transshipment strategy and multiple sourcing, are thus built, and the corresponding stochastic programmes are solved using the sample average approximation method. Through a numerical investigation conducted with several generated instances and an empirical investigation based on the case of a major French retailer’s distribution network, we show the substantial benefit of lateral transshipments and multiple sourcing in reducing the expected total costs of the distribution network. 相似文献
The transport of pharmaceutical or cosmetic active substances that are not soluble in water requires their solubilisation or encapsulation in a suitable dosage form. A material combining the solubilising properties of β-cyclodextrins and the biocompatibility of silicone has been prepared as an aqueous emulsion and used for the encapsulation of an antifungal molecule.
β-cyclodextrins have been chemically grafted to the poly(methylhydrosiloxane) polymer or poly(methylhydrosiloxane-co-dimethylsiloxane) copolymer through hydrosilylation reaction. The multi-step synthesis includes the regioselective attachment of tosyl group to one of the primary hydroxyls, its conversion into allylic derivative and subsequent acetylation of the remaining hydroxyl groups. The final step consists in grafting the cyclodextrin derivative to silicone polymer by means of hydrosilylation reaction.
Such polymers that bear peracetylated β-cyclodextrins have been emulsified by the “spontaneous emulsification” method, giving stable emulsions with sizes ranging between 200 and 500 nm. The emulsions could encapsulate the antifungal substance griseofulvin inside the β-cyclodextrin cavity by formation of inclusion complex. The encapsulation rate was limited to the 1:1 stoichiometry of the complex. Supplementary amount of griseofulvin could not be encapsulated and slowly precipitated as crystalline particles. Emulsions of silicone oil investigated as reference formulations did not incorporate even a small amount of griseofulvin. 相似文献