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  • MDPI AG  (26)
  • 1
    Online Resource
    Online Resource
    Wood−Derived Polymers from Olefin−Functionalized Lignin and Ethyl Cellulose via Thiol–Ene Click Chemistry
    MDPI AG ; 2023
    In:  Polymers Vol. 15, No. 8 ( 2023-04-18), p. 1923-
    Details
    In: Polymers, MDPI AG, Vol. 15, No. 8 ( 2023-04-18), p. 1923-
    Abstract: Lignin and cellulose derivatives have vast potential to be applied in polymer materials. The preparation of cellulose and lignin derivatives through esterification modification is an important method to endow cellulose and lignin with good reactivity, processability and functionality. In this study, ethyl cellulose and lignin are modified via esterification to prepare olefin−functionalized ethyl cellulose and lignin, which are further used to prepare cellulose and lignin cross−linker polymers via thiol–ene click chemistry. The results show that the olefin group concentration in olefin−functionalized ethyl cellulose and lignin reached 2.8096 mmol/g and 3.7000 mmol/g. The tensile stress at break of the cellulose cross−linked polymers reached 23.59 MPa. The gradual enhancement in mechanical properties is positively correlated with the olefin group concentration. The existence of ester groups in the cross−linked polymers and degradation products makes them more thermally stable. In addition, the microstructure and pyrolysis gas composition are also investigated in this paper. This research is of vast significance to the chemical modification and practical application of lignin and cellulose.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym15081923
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2527146-5
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  • 2
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    Brain Metabolic Connectivity Patterns in Patients with Prolonged Disorder of Consciousness after Hypoxic-Ischemic Injury: A Preliminary Study
    MDPI AG ; 2022
    In:  Brain Sciences Vol. 12, No. 7 ( 2022-07-07), p. 892-
    Details
    In: Brain Sciences, MDPI AG, Vol. 12, No. 7 ( 2022-07-07), p. 892-
    Abstract: Understanding the patterns of brain glucose metabolism and connectivity in hypoxic-ischemic encephalopathy (HIE) patients with prolonged disorders of consciousness (DOC) may be of positive significance to the accurate assessment of consciousness and the optimization of neuromodulation strategy. We retrospectively analyzed the brain glucose metabolism pattern and its correlation with clinical Coma Recovery Scale-Revised (CRS-R) score in six HIE patients with prolonged DOC who had undergone 18F-deoxyglucose brain positron emission tomography scanning (FDG-PET). We also compared the differences in global metabolic connectivity patterns and the characteristics of several brain networks between HIE patients and healthy controls (HC). The metabolism of multiple brain regions decreased significantly in HIE patients, and the degree of local metabolic preservation was correlated with CRS-R score. The internal metabolic connectivity of occipital lobe and limbic system in HIE patients decreased, and their metabolic connectivity with frontal lobe, parietal lobe and temporal lobe also decreased. The metabolic connectivity patterns of default mode network, dorsal attention network, salience network, executive control network and subcortex network of HIE also changed compared with HC. The present study suggested that pattern of cerebral glucose metabolism and network connectivity of HIE patients with prolonged DOC were significantly different from those of healthy people.
    Type of Medium: Online Resource
    ISSN: 2076-3425
    URL: Article
    DOI: 10.3390/brainsci12070892
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2651993-8
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  • 3
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    Methods for Obtaining One Single Larmor Frequency, Either v1 or v2, in the Coherent Spin Dynamics of Colloidal Quantum Dots
    MDPI AG ; 2023
    In:  Nanomaterials Vol. 13, No. 13 ( 2023-07-05), p. 2006-
    Details
    In: Nanomaterials, MDPI AG, Vol. 13, No. 13 ( 2023-07-05), p. 2006-
    Abstract: The coexistence of two spin components with different Larmor frequencies in colloidal CdSe and CdS quantum dots (QDs) leads to the entanglement of spin signals, complicating the analysis of dynamic processes and hampering practical applications. Here, we explored several methods, including varying the types of hole acceptors, air or anaerobic atmosphere and laser repetition rates, in order to facilitate the obtention of one single Larmor frequency in the coherent spin dynamics using time-resolved ellipticity spectroscopy at room temperature. In an air or nitrogen atmosphere, manipulating the photocharging processes by applying different types of hole acceptors, e.g., Li[Et3BH] and 1-octanethiol (OT), can lead to pure spin components with one single Larmor frequency. For as-grown QDs, low laser repetition rates favor the generation of the higher Larmor frequency spin component individually, while the lower Larmor frequency spin component can be enhanced by increasing the laser repetition rates. We hope that the explored methods can inspire further investigations of spin dynamics and related photophysical processes in colloidal nanostructures.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano13132006
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662255-5
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  • 4
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    Rubber Seed Oil-Based UV-Curable Polyurethane Acrylate Resins for Digital Light Processing (DLP) 3D Printing
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 18 ( 2021-09-08), p. 5455-
    Details
    In: Molecules, MDPI AG, Vol. 26, No. 18 ( 2021-09-08), p. 5455-
    Abstract: Novel UV-curable polyurethane acrylate (PUA) resins were developed from rubber seed oil (RSO). Firstly, hydroxylated rubber seed oil (HRSO) was prepared via an alcoholysis reaction of RSO with glycerol, and then HRSO was reacted with isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA) to produce the RSO-based PUA (RSO-PUA) oligomer. FT-IR and 1H NMR spectra collectively revealed that the obtained RSO-PUA was successfully synthesized, and the calculated C=C functionality of oligomer was 2.27 per fatty acid. Subsequently, a series of UV-curable resins were prepared and their ultimate properties, as well as UV-curing kinetics, were investigated. Notably, the UV-cured materials with 40% trimethylolpropane triacrylate (TMPTA) displayed a tensile strength of 11.7 MPa, an adhesion of 2 grade, a pencil hardness of 3H, a flexibility of 2 mm, and a glass transition temperature up to 109.4 °C. Finally, the optimal resin was used for digital light processing (DLP) 3D printing. The critical exposure energy of RSO-PUA (15.20 mJ/cm2) was lower than a commercial resin. In general, this work offered a simple method to prepare woody plant oil-based high-performance PUA resins that could be applied in the 3D printing industry.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules26185455
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2008644-1
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  • 5
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    Online Resource
    Determination of Hexabromocyclododecane in Expanded Polystyrene and Extruded Polystyrene Foam by Gas Chromatography-Mass Spectrometry
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 23 ( 2021-11-25), p. 7143-
    Details
    In: Molecules, MDPI AG, Vol. 26, No. 23 ( 2021-11-25), p. 7143-
    Abstract: A gas chromatography-mass spectrometry (GC/MS) method for the determination of hexabromocyclododecane (HBCD) in expanded polystyrene and extruded polystyrene foam (EPS/XPS) was developed. The EPS/XPS samples were ultrasonically extracted with acetone and the extracts were purified by filtration through a microporous membrane (0.22 μm) and solid-phase extraction. The samples were analyzed using a GC/MS using the selected ion monitoring mode. The ions 157, 319 and 401 were selected as the qualitative ions, while ion 239 was chosen as the quantitative ion. An HBCD standard working solution with a concentration range of 1.0–50.0 mg/L showed good linearity. The detection limit of HBCD was 0.5 mg/kg, meeting the LPC limit ( 〈 100 or 1000 mg/kg). Six laboratories were selected to verify the accuracy of the method, and 10 samples were tested. The interlaboratory relative standard deviation range was 3.68–9.80%. This method could play an important role in controlling HBCD contamination in EPS/XPS.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules26237143
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 6
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    Is There Herd Effect in Farmers’ Land Transfer Behavior?
    MDPI AG ; 2022
    In:  Land Vol. 11, No. 12 ( 2022-12-02), p. 2191-
    Details
    In: Land, MDPI AG, Vol. 11, No. 12 ( 2022-12-02), p. 2191-
    Abstract: China’s rural land transfer market has been plagued by issues including poor information transmission, limited scale, and an incoherent structure. In this context, this study collected the data of 337 farmers in Qufu City, Shandong Province, and incorporated into the analysis the acquaintance-based nature of rural society that includes strong geographic ties. Taking the herd effect as the starting point, this paper it considers how farmers in the same geo-network affect the land transfer behavior of individual farmers, and adopts the Probit model to analyze the impact of geo-networks to verify the function of the herd effect in farmers’ land transfer behavior. Then, the IV-Probit model is applied to solve the endogenous problem of the herd effect. The results show that: (1) Farmers imitate the land transfer behavior of other farmers in the same geo-network. Geo-networks positively impact the land transfer behavior of farmers, and the herd effect is apparent in farmers’ land transfer behavior. (2) Farmers’ family background, resource endowment, and cognitive features are key factors that influencing farmers’ land transfer behavior. (3) Farmers’ land transfer behavior is more significantly influenced in groups with low and middle agricultural income than in groups with high agricultural income. This study aims to assist the government in giving full play to the positive role of the herd effect, promoting the leading role of village cadres as leader sheep, and smoothing the transmission of land transfer information. Governments should place more emphasis on developing land transfer platforms and invest more in the construction of farmland infrastructure. This paper may serve as a reference to achieve large-scale agriculture operation via land transfer and promote the prosperity of the land transfer market.
    Type of Medium: Online Resource
    ISSN: 2073-445X
    URL: Article
    DOI: 10.3390/land11122191
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
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  • 7
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    Preparation and Properties of Plant-Oil-Based Epoxy Acrylate-Like Resins for UV-Curable Coatings
    MDPI AG ; 2020
    In:  Polymers Vol. 12, No. 9 ( 2020-09-22), p. 2165-
    Details
    In: Polymers, MDPI AG, Vol. 12, No. 9 ( 2020-09-22), p. 2165-
    Abstract: Novel oil-based epoxy acrylate (EA)-like prepolymers were synthesized via the ring-opening reaction of epoxidized plant oils with a new unsaturated carboxyl acid precursor (MAAMA) synthesized by reacting maleic anhydride (MA) with methallyl alcohol (MAA). Since the employed epoxidized oils including epoxidized soybean oil (ESO), epoxidized rubber seed oil (ERSO), and epoxidized wilsoniana seed oil (EWSO) possessed epoxy values of 7.34–4.38%, the obtained epoxy acrylate (EA)-like prepolymers (MMESO, MMERSO, and MMEWSO) indicated a C=C functionality of 7.81–4.40 per triglyceride. Furthermore, effects of the C=C functionality and the addition of hydroxyethyl methacrylate (HEMA) diluent on the ultimate properties of the resulting UV-cured EA-like materials were investigated and compared with those of commercially available acrylated ESO (AESO) resins. As the C=C functionality increased, the storage modulus at 25 °C (E’25), glass transition temperature (Tg), 5% weight–loss temperature (T5), tensile strength and modulus (σ and E), and hardness of the coating for both the pure EA and EA/HEMA resins increased significantly as well. These properties indicated similar trends when comparing the EA materials with 30% of HEMA with those pure EA materials. Specially, although ERSO had a clearly lower epoxy value that ESO, both the UV-cured pure MMERSO and MMERSO/HEMA materials showed much better E’25, Tg, σ, and E than their AESO counterparts, indicating that the MAAMA modification of epoxidized plant oils was much more effective than the modification of acrylic acid to achieve high-performance oil-based epoxy acrylate resins.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym12092165
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
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  • 8
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    Citrullus colocynthis (L.) Schrad.: A Promising Pharmaceutical Resource for Multiple Diseases
    MDPI AG ; 2023
    In:  Molecules Vol. 28, No. 17 ( 2023-08-24), p. 6221-
    Details
    In: Molecules, MDPI AG, Vol. 28, No. 17 ( 2023-08-24), p. 6221-
    Abstract: Citrullus colocynthis (L.) Schrad. (Cucurbitaceae) is widely distributed in the desert areas of the world. The fruit bodies of C. colocynthis are recognized for their wide range of nutraceutical potential, as well as medicinal and pharmaceutical uses. The plant has been reported for various uses, such as asthma, bronchitis, cancer, colic, common cold, cough, diabetes, dysentery, and jaundice. The fruit has been extensively studied for its biological activities, which include insecticide, antitumor, and antidiabetic effects. Numerous bioactive compounds have been reported in its fruit bodies, such as essential oils, fatty acids, glycosides, alkaloids, and flavonoids. Of these, flavonoids or caffeic acid derivatives are the constituents associated with the inhibition of fungal or bacterial growth, whereas eudesmane sesquiterpenes or sesquiterpene lactones are most active against insects, mites, and nematodes. In this review, the scientific evidence for the biological activity of C. colocynthis against insecticide, cytotoxic, and antidiabetic effects is summarized.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules28176221
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
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  • 9
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    Online Resource
    Simultaneous Identification and Dynamic Analysis of Saccharides during Steam Processing of Rhizomes of Polygonatum cyrtonema by HPLC–QTOF–MS/MS
    MDPI AG ; 2018
    In:  Molecules Vol. 23, No. 11 ( 2018-11-02), p. 2855-
    Details
    In: Molecules, MDPI AG, Vol. 23, No. 11 ( 2018-11-02), p. 2855-
    Abstract: The sweet rhizomes of Polygonatum cyrtonema are widely used as a tonic and functional food. A sensitive and rapid analytical method was developed for simultaneous identification and dynamic analysis of saccharides during steam processing in P. cyrtonema using HPLC–QTOF–MS/MS. Fructose, sorbitol, glucose, galactose, sucrose, and 1-kestose were identified, as well as a large number of oligosaccharides constituted of fructose units through β-(2→1) or β-(2→6). Polysaccharides and oligosaccharides were decomposed to monosaccharides during a steaming process, since the contents of glucose, galactose, and fructose were increased, while those of sucrose, 1-kestose, and polysaccharides were decreased. The high content of fructose was revealed to be the main determinant for increasing the level of sweetness after steaming. The samples of different repeated steaming times were shown to be well grouped and gradually shift along the PC1 (72.4%) axis by principal component analysis. The small-molecule saccharides, especially fructose, could be considered as markers for the steaming process of rhizomes of P. cyrtonema.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules23112855
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
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  • 10
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    The Use of Cultivated Land for Multiple Functions in Major Grain-Producing Areas in Northeast China: Spatial-Temporal Pattern and Driving Forces
    MDPI AG ; 2022
    In:  Land Vol. 11, No. 9 ( 2022-09-03), p. 1476-
    Details
    In: Land, MDPI AG, Vol. 11, No. 9 ( 2022-09-03), p. 1476-
    Abstract: The increasing scarcity of cultivated land resources necessitates the continuous change in cultivated land functions. Cultivated land has gradually changed from being used for a single function to multiple functions. The use of cultivated land for multiple functions has become an important way to achieve the sustainable use, management, and protection of cultivated land. In this, the development of different functions of cultivated land must be coordinated. Thus, clarifying the evolution trend of the use of cultivated land for various functions, calculating the coupling and coordination degrees of these multiple functions, and identifying the driving factors in these uses play important roles in realizing the orderly development of cultivated land multifunctionality. This paper defined multifunctioning cultivated land as containing a production function, a social function, and an ecological function. Based on the socioeconomic panel data and geospatial data of Heilongjiang, Jilin, and Liaoning, which are the major grain-producing areas of northeast China, in the years 2005, 2010, 2015, and 2020 we calculated the multiple function coupling coordination degree of cultivated land using the Coupling Coordination Degree Model and identified the driving forces in the evolution of the spatial-temporal pattern of cultivated land multifunctionality using Geodetector. The results show that from 2005 to 2020, there were significant regional differences in terms of the production, social, and ecological functions of cultivated land in the research areas. The multifunctional coupling coordination degree of cultivated land in the study areas was gradually improved. The spatial-temporal evolution of the multifunctional coupling coordination degree of cultivated land was found to mainly be influenced by the level of agricultural development, such as the level of per capita disposable income and the rate of effective irrigation of cultivated land. The government should attempt to guarantee the comparative benefits of agricultural production to increase the income level of farmers; increase investment in agricultural infrastructure construction to improve the level of agriculture development; and implement a strict farmland protection policy to achieve the continuous improvement of the productivity of cultivated land, realize the ordered development of coupling, and improve the coordination of the use of cultivated land for multiple functions. The results of this study are applicable not only to northeast China but also to other major grain-producing areas that are under pressure to protect their cultivated land and achieve the suitable use of cultivated land.
    Type of Medium: Online Resource
    ISSN: 2073-445X
    URL: Article
    DOI: 10.3390/land11091476
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2682955-1
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