CO
2
-Responsive polymer materials have received enormous attention in recent years, since CO
2
as a new trigger has many advantages such as abundant availability, low cost, energy-saving, ...environment-friendly, non-toxic, good reversibility as well as great biocompatibility. In this review, we first discuss the virtues of CO
2
-responsiveness by comparing with traditional stimuli-sensitive materials that respond to pH, light, or redox stimuli. Then, the chemical fundamentals of CO
2
-responsive polymer materials are revealed including recently discovered "unexpected" CO
2
-sensitive features. Recent progress of CO
2
-responsive polymer materials is highlighted followed by various CO
2
-responsive "smart" polymer systems. Finally, challenges and outlooks in this area are discussed.
This paper reviews the chemical fundamentals of CO
2
-responsive polymers as well as the latest reported "smart" material systems switched by CO
2
.
Cellulose is inherently resistant to breakdown, and the native crystalline structure (cellulose I) of cellulose is considered to be one of the major factors limiting its potential in terms of ...cost-competitive lignocellulosic biofuel production. Here we report the impact of ionic liquid pretreatment on the cellulose crystalline structure in different feedstocks, including microcrystalline cellulose (Avicel), switchgrass ( Panicum virgatum ), pine ( Pinus radiata ), and eucalyptus ( Eucalyptus globulus ), and its influence on cellulose hydrolysis kinetics of the resultant biomass. These feedstocks were pretreated using 1-ethyl-3-methyl imidazolium acetate (C2mimOAc) at 120 and 160 °C for 1, 3, 6, and 12 h. The influence of the pretreatment conditions on the cellulose crystalline structure was analyzed by X-ray diffraction (XRD). On a larger length scale, the impact of ionic liquid pretreatment on the surface roughness of the biomass was determined by small-angle neutron scattering (SANS). Pretreatment resulted in a loss of native cellulose crystalline structure. However, the transformation processes were distinctly different for Avicel and for the biomass samples. For Avicel, a transformation to cellulose II occurred for all processing conditions. For the biomass samples, the data suggest that pretreatment for most conditions resulted in an expanded cellulose I lattice. For switchgrass, first evidence of cellulose II only occurred after 12 h of pretreatment at 120 °C. For eucalyptus, first evidence of cellulose II required more intense pretreatment (3 h at 160 °C). For pine, no clear evidence of cellulose II content was detected for the most intense pretreatment conditions of this study (12 h at 160 °C). Interestingly, the rate of enzymatic hydrolysis of Avicel was slightly lower for pretreatment at 160 °C compared with pretreatment at 120 °C. For the biomass samples, the hydrolysis rate was much greater for pretreatment at 160 °C compared with pretreatment at 120 °C. The result for Avicel can be explained by more complete conversion to cellulose II upon precipitation after pretreatment at 160 °C. By comparison, the result for the biomass samples suggests that another factor, likely lignin−carbohydrate complexes, also impacts the rate of cellulose hydrolysis in addition to cellulose crystallinity.
Although many studies exist on mobile robot path planning, the disadvantages of complex algorithms and many path nodes in logistics warehouses and manufacturing workshops are obvious, mainly due to ...the inconsistency of map environment construction and pathfinding strategies. In this study, to improve the efficiency of mobile robot path planning, the Delaunay triangulation algorithm was used to process complex obstacles and generate Voronoi points as pathfinding priority nodes. The concept of the grid was used to extract obstacle edges to provide obstacle avoidance strategies for robot pathfinding. Subsequently, the search for priority and regular path nodes used the improved A-star (A*) algorithm. The dynamic fusion pathfinding algorithm (DFPA), based on Delaunay triangulation and improved A*, was designed, which realizes the path planning of mobile robots. MATLAB 2016a was used as the simulation software, to firstly verify the correctness of the DFPA, and then to compare the algorithm with other methods. The results show that under the experimental environment with the same start point, goal point, and number of obstacles, the map construction method and pathfinding strategy proposed in this paper reduce the planned path length of the mobile robot, the number of path nodes, and the cost of overall turn consumption, and increase the success rate of obtaining a path. The new dynamic map construction method and pathfinding strategy have important reference significance for processing chaotic maps, promoting intelligent navigation, and site selection planning.
Biofilms and the rapid evolution of multidrug resistance complicate the treatment of bacterial infections. Antibiofilm agents such as metallic–inorganic nanoparticles or peptides act by exerting ...antibacterial effects and, hence, do not combat biofilms of antibiotics-resistant strains. In this Letter, we show that the block copolymer DA95B5, dextran-block-poly((3-acrylamidopropyl) trimethylammonium chloride (AMPTMA)-co-butyl methacrylate (BMA)), effectively removes preformed biofilms of various clinically relevant multidrug-resistant Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE V583), and Enteroccocus faecalis (OG1RF). DA95B5 self-assembles into core–shell nanoparticles with a nonfouling dextran shell and a cationic core. These nanoparticles diffuse into biofilms and attach to bacteria but do not kill them; instead, they promote the gradual dispersal of biofilm bacteria, probably because the solubility of the bacteria–nanoparticle complex is enhanced by the nanoparticle dextran shell. DA95B5, when applied as a solution to a hydrogel pad dressing, shows excellent in vivo MRSA biofilm removal efficacy of 3.6 log reduction in a murine excisional wound model, which is significantly superior to that for vancomycin. Furthermore, DA95B5 has very low in vitro hemolysis and negligible in vivo acute toxicity. This new strategy for biofilm removal (nanoscale bacterial debridement) is orthogonal to conventional rapidly developing resistance traits in bacteria so that it is as effective toward resistant strains as it is toward sensitive strains and may have widespread applications.
Analysis of isotopes of neon and argon using the same mass spectrometer is somewhat difficult because the
40
Ar background after argon measurement can interfere with the
20
Ne determination due to ...the very similar mass-to-charge ratios of
40
Ar
++
and
20
Ne
+
. Analysis becomes even more difficult if the sample has a high abundance ratio of Ar/Ne and an extremely low amount of Ne. Here, we present a method for precise measurement of neon isotopes on a noble gas mass spectrometer (MMS) and argon isotopes on a quadruple mass spectrometer (QMS). The desorption curves of neon and argon on a charcoal trap and stainless steel trap were respectively determined, and the results demonstrated that the stainless steel trap was more suitable for the absolute separation of neon and argon despite requiring a lower temperature. The argon background effect of the MMS on the
20
Ne determination was discussed emphatically; it was found that the charcoal trap immersed in liquid nitrogen (LN) near the ion source could effectively decrease the argon background. Furthermore, the liquid level of the LN should not only be located as close to the ion source as possible but should be kept constant, which is very important for the measurement of
20
Ne with a small signal size. The ratio of CO
2
++
/CO
+
for MMS was 1.2 ± 0.3%, which enabled the correction of CO
2
++
interference in the
22
Ne determination. An artificial mixture of standard gases with an abundance ratio of argon to neon as high as 1000 was prepared. 0.1 cm
3
standard gas mixture with 5.50 × 10
−13
mol argon and 5.53 × 10
−16
mol neon was measured each time. The precisions of the isotopic ratios of neon measured by MMS were ±0.15% for
20
Ne/
22
Ne and ±1.6% for
21
Ne/
22
Ne. The precisions of the isotopic ratios of argon measured by QMS were ±0.5% for
40
Ar/
36
Ar and 4.0% for
38
Ar/
36
Ar. Although the precision of the argon isotope analysis obtained by QMS was not as good as that obtained by MMS, it fully meets the requirements for application in geochemical tracers. Moreover, this method avoids the use of the same mass spectrometer for analysis of both argon and neon, thus guaranteeing precision of the neon isotope measurements.
Through cryogenic separation by a stainless steel trap, precise Ne and Ar isotope measurement of samples with high abundance ratios of Ar/Ne and extremely low abundances of neon was achieved by a combination of MMS and QMS.
Ionic liquids (ILs) have recently been demonstrated to be highly effective solvents for the dissolution of cellulose and lignocellulosic biomass. To date, there is no definitive rationale for ...selecting ionic liquids that are capable of dissolving these biopolymers. In this work, an all-atom force field for the IL 1-ethyl-3-methylimidazolium acetate C2mimOAc was developed and the behavior of cellulose in this IL was examined using molecular dynamics simulations of a series of (1−4) linked β-d-glucose oligomers with a degree of polymerization n = 5, 6, 10, and 20. Molecular dynamics simulations were also carried out on cellulose oligomers in two common solvents, water and methanol, which are known to precipitate cellulose from IL solutions, to determine the extent and energetics of the interactions between these solvents and the cellulosic oligomers. Thermodynamic properties, such as density and solubility, as well as the two-body solute−solvent interaction energy terms, were calculated. The structural and dynamic behavior of solutions was analyzed and the conformations of cellulose oligomers were compared in ionic liquid and water mixtures. It was found that the interaction energy between the polysaccharide chain and the IL was stronger than that for either water or methanol. In addition to the anion acetate forming strong hydrogen bonds with hydroxyl groups of the cellulose, some of the cations were found to be in close contact with the polysaccharides through hydrophobic interactions. These results support the concept that the cation may play a significant role in the dissolution of cellulose by C2mimOAc. It is also observed that the preferred β-(1,4)-glycosidic linkage conformation of the cellulose was altered when dissolved in C2mimOAc as compared to that found in crystalline cellulose dispersed in water. To our knowledge, this report is the first theoretical study that addresses the key factors in cellulose dissolution using an ionic liquid.
Based on chronological and archaeobotanical studies of 15 Neolithic and Bronze Age sites from the northern Chinese Loess Plateau and southern Inner Mongolia-the agro-pastoral zone of China-we ...document changes in the agricultural system over time. The results show that wheat and rice were not the major crops of the ancient agricultural systems in these areas, since their remains are rarely recovered, and that millet cultivation was dominant. Millet agriculture increased substantially from 3000 BC-2000 BC, and foxtail millet evidently comprised a high proportion of the cultivated crop plants during this period. In addition, as the human population increased from the Yangshao to the Longshan periods, the length and width of common millet seeds increased by 20-30%. This demonstrates the co-evolution of both plants and the human population in the region. Overall, our results reveal a complex agricultural-gardening system based on the cultivation of common millet, foxtail millet, soybeans and fruit trees, indicating a high food diversity and selectivity of the human population.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In recent years, China has proposed the goal of peaking carbon dioxide emissions by 2030 and achieving carbon neutrality by 2060, which will significantly alter its existing coal-based energy mix. ...Since coal is China’s primary source of energy and the largest contributor to carbon emissions, coal reduction is an important measure toward carbon neutrality. In order to guarantee the stable development of economy and society in the process of coal reduction, the path and cost of coal reduction need to be studied in depth. Based on coal use in China, this paper examines and measures the stages and costs of coal reduction. It also gives a definition for coal reduction costs for the first time, including economic cost, environment and ecology cost, and health cost, as well as proposes a framework for analyzing the “full cost, full process, and full scenario”. We measure the cost in combination with the KAYA formula, and take into account the time value of the cost. Based on the above measurement framework, we calculate the unit coal reduction cost and estimate the coal reduction cost between CNY 454.38 and 827.1 billion.
By reviewing the development history of shale oil reservoir stimulation technology of PetroChina Company Limited (PetroChina), we have systematically summarized the main progress of shale oil ...reservoir stimulation technology of CNPC in five aspects: reservoir stimulation mechanism, fracture-controlled fracturing, geological-engineering integrated reservoir stimulation design platform, low-cost materials, and large well-pad three-dimensional development mode. It is made clear that the major stimulation technology for shale oil reservoir is the high density multi-cluster and fracture-controlled staged fracturing aiming to increase fracture-controlled reserves, lower operation costs and increase economic benefits. Based on comprehensive analysis of the challenges shale oil reservoir stimulation technology faces in three-dimensional development, stimulation parameter optimization for fracture-controlled fracturing, refracturing and low-cost stimulation technology, we proposed five development directions of the stimulation technology: (1) Strengthen the research on integration of geology and engineering to make full use of reservoir stimulation. (2) Deepen the study on fracture-controlled fracturing to improve reserves development degree. (3) Promote horizontal well three-dimensional development of shale oil to realize the production of multiple layers vertically. (4) Research refracturing technology of shale oil reservoir through horizontal well to efficiently tap the remaining reserves between fractures. (5) Develop low-cost stimulation supporting technology to help reduce the cost and increase economic benefit of oilfield development.
Some ionic liquids (ILs) have great promise as effective solvents for biomass pretreatment, and there are several that have been reported that can dissolve large amounts of cellulose. The solubilized ...cellulose can then be recovered by addition of antisolvents, such as water or ethanol, and this regeneration process plays an important role in the subsequent enzymatic saccharification reactions and in the recovery of the ionic liquid. To date, little is known about the fundamental intermolecular interactions that drive the dissolution and subsequent regeneration of cellulose in complex mixtures of ionic liquids, water, and cellulose. To investigate these interactions, in this work, molecular dynamics (MD) simulations were carried out to study binary and ternary mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate (C2mimOAc) with water and a cellulose oligomer. Simulations of a cellulose oligomer dissolved in three concentrations of binary mixtures of C2mimOAc and water were used to represent the ternary system in the dissolution phase (high C2mimOAc concentration) and present during the initial phase of the regeneration step (intermediate and low C2mimOAc concentrations). The MD analysis of the structure and dynamics that exist in these binary and ternary mixtures provides information on the key intermolecular interactions between cellulose and C2mimOAc that lead to dissolution of cellulose and the key intermolecular interactions in the intermediate states of cellulose precipitation as a function of water content in the cellulose/IL/water system. The analysis of this intermediate state provides new insight into the molecular driving forces present in this ternary system.
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