The aim of this study was to develop a derivative of chitosan as pharmaceutical excipient used in sustained-release matrix tablets of poorly soluble drugs. A water-soluble quaternary ammonium carboxymethylchitosan was synthesized by a two-step reaction with carboxymethylchitosan (CMCTS), decylalkyl dimethyl ammonium and epichlorohydrin. The elemental analysis showed that the target product with 10.27% of the maximum grafting degree was obtained. To assess the preliminary safety of this biopolymer, cell toxicity assay was employed. In order to further investigate quaternary ammonium carboxymethylchitosan application as pharmaceutical excipient, aspirin was chosen as model drug. The effect of quaternary ammonium CMCTS on aspirin release rate from sustained-release matrix tablets was examined by in-vitro dissolution experiments. The results showed that this biopolymer had a great potential in increasing the dissolution of poorly soluble drug. With the addition of CMCTS-CEDA, the final cumulative release rate of drug rose up to 90%. After 12 h, at the grade of 10, 20 and 50 cps, the drug release rate increased from 58.1 to 90.7%, from 64.1 to 93.9%, from 69.3 to 96.1%, respectively. At the same time, aspirin release rate from sustainedrelease model was found to be related to the amount of quaternary ammonium CMCTS employed. With the increase of CMCTS-CEDA content, the accumulated release rate increased from 69.1% to 86.7%. The mechanism of aspirin release from sustained-release matrix tablets was also preliminary studied to be Fick diffusion. These data demonstrated that the chitosan derivative has positive effect on drug release from sustained-release matrix tablets.
OBJECTIVE: To investigate health-related quality of life and its relationship with functional status and other related factors in victims with fractures 4 years after the 2008 Sichuan earthquake. DESIGN: A cross-sectional survey with a multi-stage random sampling method. SETTING: Five hospitals from the areas most severely affected by the 2008 Sichuan earthquake. SUBJECTS: Victims with fractures aged 14 years and older who were hospitalized in the rehabilitation departments of the 5 identified hospitals during the period 12 May 2008 to 12 May 2009. METHODS: Information on demographics, such as age, gender, marital status and educational level, functional status, working status, income, and health-related quality of life, were investigated. Manual muscle test, visual analogue scale, Modified Barthel Index and Medical Outcomes Short Form 36 (SF-36) were employed as the main outcome measures. RESULTS: A total of 243 victims with fractures were interviewed. Thirty-seven percent of the fracture victims had decreased muscle strength, 28.8% had limited range of motion, 51.8% still experienced pain, and 17.7% were dependent to different extents. With the exception of the domains vitality and mental health, the earthquake victims perceived significantly lower health-related quality of life than the local general population. Older age, being female, unmarried, low education, multiple fractures, muscle weakness, pain and being dependent were significant predictors of lower health-related quality of life. Most SF-36 subscales were negatively correlated with age, multiple fractures and pain, but positively correlated with independence in activities of daily living and income. CONCLUSION: Four years after the major Sichuan earthquake, many victims with fractures still had reduced functional status and experienced pain, and their health-related quality of life was low compared with the general population.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Ternary two-dimensional (2D) monoclinic Nb2SiTe4 has garnered significant attention for its potential applications in anisotropic photoelectronics. Yet, its intrinsic indirect bandgap nature and low hole mobility, attributed to the short Nb–Nb dimer configurations, hinder the efficient photogenerated carrier separation and transport. In this Letter, using density functional theory calculations, we demonstrate the interlayer intercalation of Si results in the formation of a metastable orthorhombic Nb2SiTe4 structure devoid of detrimental short Nb–Nb dimers. Notably, this Si intercalation leads to a remarkable reduction of hole effective masses of orthorhombic Nb2SiX4 (X = S, Se, and Te), a crucial factor for achieving high carrier mobility. Taking the orthorhombic Nb2SiTe4 monolayer as an example, the calculated hole mobility (>100 cm2 V−1 s−1) is comparable in magnitude to the respectable hole mobility observed in multiple layers of the monoclinic Nb2SiTe4. To simultaneously enhance electron and hole mobility, we establish a van der Waals junction between the monoclinic and orthorhombic Nb2SiTe4 structures, achieving high and comparable carrier mobilities. The Nb2SiTe4 junction exhibits a nearly direct bandgap of 0.35 eV, rendering it suitable for infrared light harvesting. Furthermore, carriers within the Nb2SiTe4 junction become spatially separated across different layers, resulting in an intrinsic built-in electric field, which is superior for efficient photo-generated charge separation and decreases the potential nonradiative carrier recombination. Our findings highlight the impact of cation coordination engineering on the electronic and optical properties of 2D Nb2SiTe4 and provide a feasible solution to achieve better carrier transport in low-dimensional photovoltaic functionalities.
Abstract Recently, Cu I ‐ and Ag I ‐based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb‐based halide perovskite absorbers. However, up to date, only Ag I ‐based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of Cu I ‐based analogues. Here we show that, owing to the much higher energy level for the Cu 3d 10 orbitals than for the Ag 4d 10 orbitals, Cu I atoms energetically favor 4‐fold coordination, forming [CuX 4 ] tetrahedra (X=halogen), but not 6‐fold coordination as required for [CuX 6 ] octahedra. In contrast, Ag I atoms can have both 6‐ and 4‐fold coordinations. Our density functional theory calculations reveal that the synthesis of Cu I halide double perovskites may instead lead to non‐perovskites containing [CuX 4 ] tetrahedra, as confirmed by our material synthesis efforts.
The silica beads modified by poly(N-isopropylacrylamide-co-N-acryloxysuccinimide) and heparin, which was then used as temperature-responsive affinity chromatographic stationary phase were prepared via radical polymerization.Grafting ratio of polymers grafted on surfaces was 9.45% calculated by thermogravimetric analysis (TGA) and the heparin content on surfaces was 3.6 mg/g determined by Elson-Morgan method.The packing column with the modified silica beads as the HPLC stationary phase had temperature-responsive features, which was proved by separating benzene and hydrocortisone.The results also indicated that the strong affinity interaction occurs between thrombin and the modified column, with recovery of 81.4%.The releasing time of thrombin was shortened by controlling the column temperature, which provided a fast and efficient method for protein separation.
Zero-dimensional metal halides have received wide attention due to their structural diversity, strong quantum confinement, and associated excellent photoluminescence properties. A reversible and tunable luminescence would be desirable for applications such as anti-counterfeiting, information encryption, and artificial intelligence. Yet, these materials are underexplored, with little known about their luminescence tuning mechanisms. Here we report a pyramidal coplanar dimer, (TBA)Sb2Cl7 (TBA = tetrabutylammonium), showing broadband emission wavelength tuning (585−650 nm) by simple thermal treatment. We attribute the broad color change to structural disorder induced by varying the heat treatment temperatures. Increasing the heating temperature transitions the material from long-range ordered crystalline phase to highly disordered glassy phase. The latter exhibits stronger electron−phonon coupling, enhancing the self-trapped exciton emission efficiency. The work provides a new material platform for manifold optical anti-counterfeiting applications and sheds light on the emission color tuning mechanisms for further design of stimuli-responsive materials.
Three-dimensional cubic M4M′X4 (M = Ga or In, M′ = Si, Ge, or Sn, and X = S, Se, or Te) have been proposed as photovoltaic absorber materials. Herein, we present density functional theory investigation of the stability, electronic and optical properties of M4M′X4. We find that M4M′X4 exhibit unique electronic properties. M elements lose partially both the outmost s and p electrons, whereas M′ elements only lose a small fraction of the valence electrons. As a result, the conduction band edges of M4M′X4 consist of a large contribution from the M s orbitals, leading to rather small electron effective masses. The valence bands are derived from M, M′, and X p orbitals. The band gap of this family can be tuned by selecting the combination of M and X elements. Among these semiconductors, In4GeS4, In4GeSe4, In4SnS4, and In4SnSe4 are suitable for photovoltaic applications due to their stability and suitable band gaps. However, the inclusion of scarce In may hinder their large-scale applications.
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