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Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multidentate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research.

Montmorillonite (Mt) is a hydrophilic clay mineral with a generally high cationic exchange capacity and a remarkable swellability in water. Yet the application of Mt in cosmetics, paints, polymer nanocomposites, drug delivery systems, and tissue engineering are limited due to its unfavorable swelling and dispersion in alcohol/water mixtures. Improving the swellability and dispersibility of Mt in mixtures of ethanol and water remains challenging. Here, we showed that the swellability and dispersibility of Mt in ethanol/water could be significantly enhanced when lithium-Mt (Li-Mt) was intercalated by zwitterionic surfactant lauramidopropyl betaine (LPB). The binding mechanism of the LPB intercalate to Li-Mt originated from a combination of van der Waals forces, ion-dipole interaction, and electrostatic attraction. Due to the synergistic effect of Li+and LPB, the comodified Mt (LPB-Li-Mt) exhibited excellent swellability, dispersibility, and rheological properties. The structure, morphology, zeta potential, dispersibility, and gel-forming performance of LPB-Li-Mt can be modulated by the concentrations of ethanol in ethanol/water mixtures. When the ethanol concentration increased to 75% v/v ethanol solution, the free swelling of LPB-Li-Mt remained above 80%. The results from X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray photoemission spectrometry, and small-angle X-ray scattering confirmed the full exfoliation of LPB-Li-Mt at 75% (v/v) ethanol solution. The formation of a stable colloidal LPB-Li-Mt dispersion in a mixture of ethanol/water might be derived from the association between water molecules and the Li+, the hydrophobic interaction, and the ion-dipole of ethanol with the LPB molecules. The findings provide a guide for improving dispersion and swelling of Mt and modified ones in water-miscible organic solvents.

Allyl alcohol, an industrially valuable intermediate in organic synthesis, is conventionally produced through selective hydrogenation of acrolein and hydrolysis of chloropropene. However, these processes currently face challenges due to the unsustainability of fossil feedstocks. A more sustainable production of allyl alcohol from renewable feedstock (i.e., glycerol) has been demonstrated through gas-phase catalytic reaction over metal oxide catalysts with and without external H2. Improved understanding of the reaction mechanism of glycerol to allyl alcohol conversion is an important effort to rationally design more efficient catalysts. In this work, we investigate gas-phase conversion of glycerol to allyl alcohol through consecutive dehydration and hydrogen transfer reactions over Mo–V oxides supported on acid-modified montmorillonite (HMMT). The use of HMMT as a support enables the well dispersion of metal oxide particles with nominal loadings up to 5 wt % on the catalyst surface while the acidic sites facilitate dehydration of glycerol to acrolein with ∼74% selectivity. By modulating the nominal total Mo+V loading, Mo–V/HMMT catalyst with a 10 wt % metal loading afforded allyl alcohol in 22% yield at 320 °C and ambient pressure. X-ray photoelectron spectroscopic analysis of this bifunctional catalyst in the as-prepared and post-catalysis (spent) states showed changes in the surface Mo(VI)═O species and V4+/V5+redox ratio; the latter was found to decrease due to the involvement of lower valence V4+species in the hydrogen transfer reaction of acrolein. Meanwhile, the amount of surface Mo(VI)═O species with weak electronic metal–support interaction decreases after the reaction. Catalytic tests using an aqueous acrolein feed solution suggested the role of water as a hydride donor in transfer hydrogenation of this unsaturated aldehyde to allyl alcohol, while the addition of alcohol-containing compounds, such as 2-propanol and 1,2-propanediol leads to lower allyl alcohol selectivity with time on stream. The results presented here could guide the development of improved supported Mo−V oxide catalysts and reaction systems for efficient gas-phase glycerol conversion to allyl alcohol.

The nanostructure of Ag nanoparticles (NPs) plays a critical role in their surface-enhanced Raman scattering (SERS) activity. Despite many efforts to tune the nanostructure of Ag NPs, it remains a great challenge as Ag NPs tend to agglomerate and their nanostructure is difficult to control. Herein, newly-discovered clay-surfactant-Ag+materials and interfacial processes were developed and used to prepare uniform spherical Ag@synthetic hectorite (Ag@Hct) nanomaterials for ultrasensitive SERS assay. Sodium dodecyl sulfate (SDS), an anionic surfactant, acted as a bridge to conjugate the positively charged edge of Hct NPs and Ag+viaelectrostatic interaction to form the bridging nanostructure of Hct-SDS-Ag+, which promoted the uniform dispersion of Hct NPs. Following this, Ag+was reduced to Ag0by the reductant, and Ag0grew on the surface of disc-like Hct NPs to form spherical Ag@Hct nanomaterials with an average particle size of ∼24 nm. The prepared Ag@Hct nanomaterials showed an ultrasensitive SERS response to methylene blue (MB) with a detection limit of 10−12M. The detection limit of MB in sewage was 10−11M. The prepared Ag@Hct nanomaterials also exhibited great SERS enhancement for malachite green and crystal violet. This work provides a novel and simple approach to prepare Ag@Hct nanomaterials with uniform spheres and adjustable particle size, allowing more sensitive and reproducible detection of MB.

Functional montmorillonite can be dispersed in polymer coatings and organic species and polymers can be intercalated into the interlayer space or grafted onto the surface of the functional montmorillonite. The addition of functional montmorillonite into polymer-based coatings can significantly improve anti-corrosion, refractory, super-hydrophobicity, antibacterial activity, and absorption of solar radiation by the resulting montmorillonite/polymer coatings. Montmorillonite can be functionalized for this purpose by ion exchange, intercalation, exfoliation, or combinations of these treatments. The rigid montmorillonite layers interspersed within the polymer matrix inhibit the penetration of corrosive substances, minimize the impact of high-temperature airflow, and thereby lead to strong resistance of the coating to corrosion and fire. The combination of polymers and dispersed montmorillonite nanolayers, which are modified by metal ions, metal oxides, and hydrophobic organic species, allows the resulting  composite coating to have quite a rough surface and a much smaller surface free energy so that the montmorillonite/polymer coating possesses superhydrophobicity. The interlayer space of functional montmorillonite can also host or encapsulate antibacterial substances, phase-change materials, and solar energy-absorbing materials. Moreover, it can act as a template to make these guest species exist in a more stable and ordered state. Literature surveys suggest that future work on the functional montmorillonite/polymer coatings should be targeted at the manufacture of functional montmorillonite nanolayers by finding more suitable modifiers and tuning the dispersion and funtionalities of montmorillonite in the coatings.

Efficient conversion of glycerol, an inevitable by-product in the transesterification process producing biodiesel, to acrylic acid (AA) and 1,2-propanediol (1,2-PDO) viaa cleaner process is attractive and challenging. In this work, the simultaneous production of AA and 1,2-PDO from glycerol over Cu2O/acid-activated montmorillonite (Cu2O/MMT-H) catalysts without external oxygen and hydrogen was first reported. A 100% conversion of glycerol, 72% selectivity to AA, and 10% selectivity to 1,2-PDO were obtained under optimal conditions. The nanostructure and chemical state of Cu2O and MMT-H played important roles in the conversion of glycerol. The corresponding mechanism for the oxydehydration and hydrogenolysis of glycerol to AA and 1,2-PDO over the Cu2O/MMT-H catalysts was proposed. Dehydration of glycerol occurred at the primary carbon to form acetol which was subsequently hydrogenated to form 1,2-PDO. Acrolein was obtained by a dehydration reaction of glycerol at secondary carbon, followed by the oxidation of acrolein to AA. The Cu2O/MMT-H-150 catalysts were reused three times without significant deactivation and structural changes. This work provides a new route for producing AA and 1,2-PDO simultaneously from glycerol in a one-pot way.

Montmorillonite (Mnt)-based solid acids have a wide range of applications in catalysis and adsorption of pollutants. For such solid acids, the acidic characteristic often plays a significant role in these applications. The objective of the current study was to examine the effects of H3PO4-activation and supporting WO3on the textural structure and surface acidic properties of Mnt. The Mnt-based solid acid materials were prepared by H3PO4treatment and an impregnation method with a solution of ammonium metatungstate (AMT) and were examined as catalysts in the dehydration of glycerol to acrolein. The catalysts were characterized by nitrogen adsorption-desorption, powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance ultraviolet-visible (DR UV-Vis) spectroscopy, temperature programmed desorption of NH3(NH3-TPD), diffuse reflectance Fourier-transform infrared (DR FTIR) spectroscopy of adsorbed pyridine, and thermogravimetric (TG) analyses. The phosphoric acid treatment of Mnt created Brönsted and Lewis acid sites and led to increases in specific surface areas, porosity, and acidity. WO3species influenced total acidity, acid strength, the numbers of Brönsted and Lewis acid sites, and catalytic performances. A high turnover frequency (TOF) value (31.2 h−1) based on a maximal 60.7% yield of acrolein was reached. The correlation of acrolein yield with acidic properties indicated that the cooperative role of Brönsted and Lewis acid sites was beneficial to the formation of acrolein and a little coke deposition (<3.3 wt.%). This work provides a new idea for the design of solid acid catalysts with cooperative Brönsted and Lewis acidity for the dehydration of glycerol.

Organo-montmorillonite (OMnt) has wide applications in paints, clay-polymer nanocomposites, biomaterials, etc. In most cases, the dispersibility and swellability of OMnt dictate the performance of OMnt in the target products. Previous studies have revealed that the properties can be improved when multiple organic species are co-introduced into the interlayer space of montmorillonite (Mnt). In the present study, single surfactant erucylamide (EA), dual-surfactants cetyltrimethyl ammonium bromide (CTAB) and octadecyltrimethyl ammonium chloride (OTAC), and ternary-surfactants EA, CTAB, and OTAC were co-introduced into Mnt by solution intercalation. The resulting OMnts were characterized by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry-differential thermogravimetry (TG-DTG), water contact-angle tests, scanning electronic microscopy (SEM), laser particle-size analysis, and swelling indices. Mnt co-modified by ternary CTAB, OTAC, and EA led to a large d001value (4.20 nm), surface hydrophobicity with a contact angle of 95.6°, swellability (50 mL/g) with small average particle sizes (2.1−2.8 μm) in xylene, and >99% of the OMnt particles were kept as <5 μm in deionized water. The formation of EA-modified-Mnt was proposed according to hydrophobic affinity, hydrogen bonding, and van der Waals forces. The nanoplatelets of the CTA+, OTA+, and EA co-modified OMnts in xylene were assembled into a house-of-cards structure by face-to-edge and edge-to-edge associations. The electrostatic attractions, electrostatic and steric repulsions, and hydrophobic interactions were responsible for the good dispersibility of OMnt in xylene. The ternary surfactant co-modified OMnt with high dispersion and swellability will make OMnt better suited for real-world applications.

Catalytic glycerol dehydration provides a sustainable route to produce acrolein because glycerol is a bioavailable platform chemical. However, in this process catalysts are rapidly deactivated due to coking. This paper examines and discusses recent insights into coking of catalysts during catalytic glycerol dehydration. The nature and location of coke and the rate of coking depend on feedstock, operating conditions, and the acidity and pore structure of the solid catalysts. Several methods have been suggested for inhibiting the coking and slowing the deactivation of catalyst, including (1) cofeeding of oxygen, (2) tuning of the pore size of the solid acid catalysts, (3) doping noble metals (Ru, Pt, Pd) into the solid acid catalysts, and (4) designing new reactors. The present methods for inhibiting coking are still unsatisfactory. The deactivated catalysts can be regenerated by removing coke. Nevertheless, the rapid deactivation of the regenerated catalyst remains problematic. The literature survey indicates that the exact chemical compositions of the coke on the catalyst during glycerol dehydration remain elusive. The thermodynamics, kinetics, and mechanism of coking need to be probed so as to advance the development of a catalyst with high activity, selectivity, and resistance to coking to put the catalytic glycerol dehydration into practice.

In order to achieve the intelligent dissemination of remote sensing image, the primary task is to establish a suitable user profile. In this paper, we proposed a novel approach of modeling user demand preferences, and took into account the multiple interests and the time factors. And we presented some computing methods of feature preference including time, space, image parameters, etc. At last, the simulation example shows the feasibility and effectiveness of the designed user demand preference model.

Traditional paper labels on the supermarkets shelves are of many shortcomings such as the high error rate, high losing rate, increasing cost and unrealizable realtime-updating caused by manual management. In order to overcome these shortcomings, this paper aims to design a new Electronic Shelf Label system. Firstly, the overall framework is introduced. Then an ultra-low-power ESL and wireless communication base station modules are studied respectively. The MAC and router protocols are also designed based on Wireless Sensor Network (WSN) to meet the requirement of low power consumption and real-time price update. The Electronic Shelf Label system can improve the efficiency of the label management greatly and enhance customers experiences thus has a wide prospect of application.

Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} With the rapid progress of standardization of 3GPP’s LTE (Long Term Evolution) and LTE-Advanced, many research attentions have been focused on the link level evaluations of the 3GPP LTE systems, so as to demonstrate the rationality of novel transmission techniques. Different from theoretical studies, incorporating novel transmission techniques in to the LTE communication systems may affect many parts of the systems, such as signaling process, reference signal design, feedback link design, and compatibility, etc. Link level studies might be too simple to evaluate the benefits of these novel techniques to the entire system. On the other hand, system level simulation concentrates on the performance of the entire network with tens of cells and hundreds to thousands of users. It is possible to illustrate the actual performance of a LTE system by simulations designed from a system standpoint. Since the simulated system is quite large, one can understand the speed of simulation is very important for system level simulation platform. In this paper, we propose a design of Matlab-based 3GPP LTE system level simulator, which makes use of parallel computing techniques supported by NVidia GeForce GTX 260 graphic card. Our simulation experience shows that the simulation time reduces by nearly 1/3 after employing parallel computing techniques.

To convert glycerol, a by-product of biodiesel, into value-added fine chemicals is of great industrial and economic importance and represents a great challenge. This paper reports the influence of various metal elements (M = Ni, Zn, Cu, Co, etc.) incorporated into MgAl layered double hydroxide (LDH) materials used as catalysts for the liquid phase oxidation of glycerol to fine chemicals. The catalytic behaviour was also studied and discussed in terms of structure and texture of the synthesized materials that were determined using PXRD, FE-SEM, TEM, TG-DTA, FTIR, XPS and nitrogen adsorption–desorption isotherms. The results revealed that CuAlMg LDH materials are active in converting glycerol to glyceric acid (GLYAC) and formic acid, while yielding oxalic and hydroxyehthanoic acid. The selectivity to glyceric acid remarkably increased over Cu-containing catalysts, compared with those over similar materials with the addition of Ni, Zn, Co metal elements. The increase of Cu content not only affects the catalyst activity but also the selectivity. Moreover, an improvement of activity and selectivity was found on calcined CuAlMg samples. The calcined catalysts, with a Cu : Al : Mg molar ratio of 20 : 100 : 200, exhibited superior performances with a 97.3% conversion of glycerol and a 70% glyceric acid selectivity. It was concluded that the nature of the metal added to the LDH structure, such as Cu as active sites, in combination with the chemical state and microenvironment in calcined and uncalcined materials significantly affects the catalytic performance of the synthesized catalysts in the liquid phase oxidation of glycerol in terms of product activity and distribution.

The surface-grafted titanium MCM-41 materials were prepared by anchoring titanocene onto the inner walls of MCM-41. The materials were characterized by powder X-ray diffraction (XRD), N2 adsorption–desorption isotherm and diffuse reflectance UV–visible (UV–vis) spectroscopies. The catalytic properties of Ti-MCM-41 were tested in oxidation of 4-tert-butyltoluene with tert-butylhydroperoxide (TBHP) in liquid phase. MCM-41 with loading 4.8mol% Ti gave the maximal conversions of 23.6% of 4-tert-butyltoluene with a complete selectivity to 4-tert-butylbenzaldehyde.

Abstract: Objective: To investigate the neoplasm lymphatic metastasis-associated genes and its molecular mechanisms. Methods: 22690 mouse genome cDNA microarrays (including 14500 known genes and 4371 ESTs) were used to compare and analyze the gene expression profiles of mouse hepatocellular carcinoma cell lines Hca-F (highly lymphatic metastasis potential) and Hca-P (low potential). Results: 901 genes and 129 ESTs were up-regulated at least 2-fold in Hca-F cell. 33 genes showing significant alterations in expression were presented, including endoglin (EDG), MCAM, Cdc42ep5, F2r, D7Ertd458e, Serpin h1 (HSP47), AXL, Areg and so on. These genes have functions of angiogenesis, cell adhesion, signal transduction, cell motility, chaperone activity, protein kinase activity and receptor binding. Conclusion: cDNA microarray combined with lymphatic metastasis models might contribute new methods and clues to the neoplasm lymphatic metastasis research. Some overexpressed genes might provide novel clues to the molecular mechanisms of neoplasm lymphatic metastasis.

A frequency-domain approach to arbitrary finite spectrum assignment for multivariable delay systems is developed, and a practical example is presented for illustration.

New results on the solution of the optimal regulation of non-linear systems are obtained. A closed form of the series solution of the problem is given, and this makes it possible to calculate the coefficient matrix in the series solution automatically, using a computer.

The problem of designing a robust controller for a multivariable system with significant uncertainty is considered. In particular, the class of uncertainty is represented by a set of finite demensional linear time-invariant models of the system. A physically realizable, finite demensional linear time-invariant controller in unit feedback configuration is designed such that the resulting feedback system simultaneously satisfies performance objectives for all models in the set. The performance objectives considered include not only stability but also regulation, tracking, weak interaction and desirable transcient behaviour. A new approach to a robust controller design which reaches the above objectives is developed in a frequency domain setting, and its effectiveness of this approach is verified by the design and simulation of a papermachine control system. The result exhibits quite satisfactory performances and strong robustness.

A general characterization of decentralized fixed modes is developed with the use of determinant theory. The main issue is resolved through the introduction of a new concept - the structure-zero minor which exhibits the complete structural features of a given control structure. Examples are presented for illustration.

A dynamic model of a saper machine is built by the mechanismic analysis and some mathematical treatments, and a new frequency response approach to multivariable control system design is developped by optimization technique and applied to the design of a basis weight and moisture content control system. This system offers satisfactory technical performances and significant economical profits.

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