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Although reduction of highly mobile U(VI) to less soluble U(IV) has been long considered an effective approach to in situ environmental remediation of uranium, candidate reducing agents are largely limited to Fe-based materials and microbials. The importance of titanium-containing compounds in natural uranium ore deposits suggests a role for titanium in uranium migration. Herein, for the first time, a two-dimensional transition metal carbide, TiCT , is shown to efficiently remove uranium via a sorption-reduction strategy. Batch experiments demonstrate that TiCT exhibits excellent U(VI) removal over a wide pH range, with an uptake capacity of 470 mg g at pH 3.0. The mechanism for U(VI) to U(IV) reduction by TiCT was deciphered by X-ray absorption spectroscopy and diffraction and photoelectron spectroscopy. The reduced U(IV) species at low pH is identified as mononuclear with bidendate binding to the MXene substrate. At near-neutral pH, nanoparticles of the UO phase adsorb to the substrate with some TiCT transformed to amorphous TiO. A subsequent in-depth study suggests TiCT materials may be potential candidates for permeable reactive barriers in the treatment of wastewaters from uranium mining. This work highlights reduction-induced immobilization of U(VI) by TiCT MXene including a pH-dependent reduction mechanism that might promote applications of titanium-based materials in the elimination of other oxidized contaminants.

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With the advances in optical technology, the span of a broadband access network using Passive Optical Network (PON) technology can be increased from today's standard of 20 km to 100 km or higher, and thereby serve a lot more users. Such an extended-reach PON is known as SuperPON in the literature, and we call it a Long-Reach PON (LR-PON). A major challenge in LR-PON is that the propagation delay (for data as well as control signals) between the telecom central office (CO) and the end user is increased by a very significant amount. Now, traditional PON algorithms for scheduling the upstream transmission, such as dynamic bandwidth allocation (DBA) algorithms, may not be sufficient; actually, they may lead to degraded performance because of the long delay of the CO-toUsers "control loop." This challenge motivates us to propose and study a multi-thread polling algorithm to effectively and fairly distribute the upstream bandwidth dynamically. This algorithm exploits the benefits of having multiple polling processes running simultaneously and enabling users to send bandwidth requests before receiving acknowledgement from the CO. We compare the proposed algorithm with traditional DBA, and show its advantage on average packet delay. We then analyze and optimize key parameters of the algorithm, such as initiating and tuning multiple threads, inter-thread scheduling, and fairness among users. Numerical results demonstrate the algorithm's advantage to decrease the average packet delay and improve network throughput under varying offered loads.Index Terms-Broadband access network, long-reach PON (LR-PON), multi-thread polling, simulation and modeling.

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Environmental contamination by 99 Tc(VII) from radioactive wastewater streams is of particular concern due to the long half-life of 99 Tc and high mobility of pertechnetate. Herein, we report a novel MXene-polyelectrolyte nanocomposite with three-dimensional networks for enhanced removal of perrhenate, which is pertechnetate simulant. The introduction of poly(diallyldimethylammonium chloride) (PDDA) regulates the surface charge and improves the stability of Ti 2 CT x nanosheet, resulting in Re(VII) removal capacity of up to 363 mg g −1 , and fast sorption kinetics. The Ti 2 CT x /PDDA nanocomposite furthermore exhibits good selectivity for ReO 4 − when competing anions (such as Cl − and SO 4 2− ) coexist at a concentration of 1800 times. The immobilization mechanism was confirmed as a sorption-reduction process by batch sorption experiments and X-ray photoelectron spectroscopy. The pH-dependent reducing activity of Ti 2 CT x /PDDA nanocomposite toward Re(VII) was clarified by X-ray absorption spectroscopy. As the pH increases, the local environment gradually changes from octahedralcoordinated Re(IV) to tetrahedral-coordinated Re(VII). The overall results suggest that Ti 2 CT x /PDDA nanocomposite may be a promising candidate for efficient elimination of Tc contamination. The reported surface modification strategy might result in applications of MXene-based materials in environmental remediation of other oxidized anion pollutants. results for Re(VII) sequestration should motivate development of Ti-based MXenes as novel materials for reduction of Tc(VII) with in situ incorporation as Tc(IV).

Abstract. Pterostilbene, being extracted from many plants, has significant biological activities in preventing cancer, diabetes, and cardiovascular diseases so as to have great potential applications in pharmaceutical fields. But the poor solubility and stability of pterostilbene strictly restrained its applications. As a good protection and oral delivery system, an optimal nanoemulsion for pterostilbene was developed by using low-energy emulsification method. Systematic pseudo-ternary phase diagrams have been studied in optimization of nanoemulsion formulations. The prepared pterostilbene nanoemulsion was characterized by transmission electron microscope, Fourier transform Raman spectrum, and laser droplet size analyzer. Nanoemulsion droplets are circular with smooth margin, and the mean size is 55.8± 10.5 nm. The results illustrated that the nanoemulsion as oral delivery system dramatically improved the stability and solubility of pterostilbene, and in vitro release of pterostilbene was significantly improved (96.5% in pH 3.6 buffer; 13.2% in pH 7.4 buffer) in comparison to the pterostilbene suspension (lower than 21.4% in pH 3.6 buffer; 2.6% in pH 7.4 buffer).

Reaction of LAl[eta2-(CSiMe3)2] (L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) with carbon monoxide and tert-butyl isocyanide afforded unique AlC3 aluminacyclobutenes via insertion into one of the aluminium-carbon bonds.