Left atrial (LA) functional analysis has an established role in assessing left ventricular diastolic function. The current standard echocardiographic parameters used to study left ventricular diastolic function include pulsed-wave Doppler mitral inflow analysis, tissue Doppler imaging measurements, and LA dimension estimation. However, the above-mentioned parameters do not directly quantify LA performance. Deformation studies using strain and strain-rate imaging to assess LA function were validated in previous research, but this technique is not currently used in routine clinical practice. This review discusses the history, importance, and pitfalls of strain technology for the analysis of LA mechanics.
Polyelectrolyte-polyelectrolyte complexes/multiwall carbon nanotubes (PECs/MWCNTs) nanocomposites have not been prepared until now because PECs are generally insoluble and infusible. In this work, solution-processable PEC/MWCNT nanocomposites and their membranes were prepared by in situ incorporation of MWCNTs into bulk PECs. The ionic complexation between poly(diallyldimethylammonium chloride) (PDDA) and sodium carboxymethyl cellulose (CMCNa) in the presence of MWCNTs was followed by z potential and optical transmittance measurements. Structures of PEC/MWCNT nanocomposites were characterized by FT-IR, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). It is found that MWCNTs are encapsulated by a layer of PEC and dispersed in a PEC matrix mainly on a single nanotube level. Mechanical properties of the nanocomposite membrane loaded with 7 wt% MWCNTs are greatly improved, showing 2.6 times higher tensile strength and 1.8 times higher modulus as compared with that of the pristine PEC. PEC/MWCNT nanocomposite membranes also display very high performance in pervaporation dehydration of isopropanol. This high pervaporation performance is reproducible with cycling feed temperatures and stable with increasing operation time up to 20 days.
Highly intergrown mordenite membranes were rapidly prepared on seeded aluminum supports by microwaveassisted synthesis. Both the thicknesses of the zeolite layer and the sizes of the zeolite crystals of the mordenite membranes were highly dependent on the synthesis time. With a SiO 2 :0.08Al 2 O 3 :0.2Na 2 O:0.1NaF:35H 2 O precursor synthesis gel, a compact and 0.75 μm thick mordenite crystal layer was successfully prepared on the aluminum support at 170 °C for 3 h. The as-synthesized mordenite membrane exhibited excellent water perm-selectivity and long-term stability for dehydration of alcohol/water, acetic acid/water, and acetic acid/ethanol/water/ethyl ester mixtures by pervaporation. For dehydration of 90 wt % acetic acid/water solution, the corresponding flux and separation factor (water over acetic acid) of the membrane remained at 0.44 kg•m −2 •h −1 and 2300, respectively, at 75 °C even after 59 days of immersion.
Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)−1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol−1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.
A continuous intergrown silicalite zeolite membrane with high pervaporation (PV) performance was successfully prepared on seeded tubular mullite supports in ultradilute solution with a H 2 O/SiO 2 ratio of 800 and an inexpensive template of tetrapropylammonium bromide (TPABr) instead of tetrapropylammonium hydroxide (TPAOH). Several parameters were systematically investigated to evaluate their influence on crystallization and PV performance of the membranes, including the H 2 O/SiO 2 ratio, template type, alkalinity, synthesis temperature, crystallization time, and silica source. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and PV tests were used to characterize the as-synthesized membranes. The crystal growth and separation quality of the silicalite membranes were very sensitive to the H 2 O/SiO 2 ratio and alkalinity in the precursor solution and synthesis temperature. Under the optimized synthesis conditions, the outer surface of support was fully covered with well-intergrown silicalite zeolite layer to form the zeolite membrane. For silicalite membrane prepared with the typical molar composition of synthesis solutions of 1SiO 2 /0.1TPABr/0.2TPAOH/800H 2 O at 180 °C for 16 h, the flux and separation factor are achieved to 1.91 kg•m −2 •h −1 and 66 for a 5 wt % ethanol/water mixture at 60 °C, respectively. Moreover, the membrane prepared with pure TPABr template instead of TPAOH in ultradilute solution also showed the high PV performance with the flux of 1.77 kg•m −2 •h −1 and separation factor of 63 under the same tests conditions. Due to the utilization of ultradilute precursor and cheap organic template to prepare the silicalite membrane on cheap mullite supports with high PV performance, the present developed technique could reduce the chemical consumption and decrease the costs of membrane toward an organic/water mixture separation.
A two-step procedure was adopted to prepare cellulose-based polyelectrolyte complexes (PECs) nanoparticles dispersed in water. First, an aqueous solution of a weak anionic polyelectrolyte of sodium carboxymethyl cellulose (CMCNa) was mixed with four types of cationic polyelectrolytes (poly 2-methacryloyloxy ethyl trimethylammonium chloride (PDMC), cationic cellulose, poly diallyldimethylammonium chloride (PDDA), chitosan (CS)) in HCl aqueous solutions. Four types of CMCNa-based PEC solids (CMCNa-PDMC, CMCNa-cationic cellulose, CMCNa-PDDA and CMCNa-CS), were obtained, purified and dried. Second, these PECs were re-dispersed in NaOH aqueous solutions. PEC solids and their aqueous dispersions were characterized by FT-IR, wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and dynamic light scattering (DLS), respectively. It was found that well grown fractal patterns (referred to as fractal ''trees'') with diameters ranging from 5-300 mm for the four PECs were obtained after their aqueous dispersions were dried on silicon wafers or glass slides at 30 C. This PECs interfacial self-assembly phenomenon is interesting but not shown in literature, even though various other PECs dispersions have also been dried in the similar way. Fractal dimensions of these fractal ''trees'' were calculated and their structures were characterized by polarized light microscopy (PLM), filed emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The formation mechanism of these fractal ''trees'' was tentatively examined by time-dependent FESEM. Moreover, effects of drying temperature, PEC concentration and solvent composition on fractal ''trees'' formation were studied. Potential applications of the fractal pattern formation in fields such as fast bottom-up nanofabrication, surface patterning and membrane separation were discussed. IntroducationPattern formation of polymers is important from both scientific and applied points of view. 1 Besides myriads of Euclid geometric patterns that have been discovered, self-similar fractal patterns 2 of polymers have recently attracted attention.  Most of these fractal patterns occur during crystallization.  For example, nonequilibrium crystallizations of poly(3-caprolactone), 4 low molecular weight poly(ethyl oxide), 5 polymethyl methacrylate 6 and isotactic poly(styrene) 7 can produce fractal or dendritic crystalline morphologies. Fractal patterns of polymers are important because they usually occur in a nonequilibrium environment which is closer to that of real applications 12 and can be utilized in tuning structures of polymers on multi-scales. 8 However, compared with those abundant fractal structures of inorganic salts, 13 fractal patterns of polymers are still very few. Especially, fractal patterns of polymers driven by forces other than crystallization are reported less. 8,10,11 Polyelectrolyte-polyelectrolyte complexes (PECs) are formed due to the ionic interaction between oppositely charged polyelectrol...
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