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Membrane Morphology (membrane + morphology)
Selected AbstractsEffects of membrane thickness and heat treatment on the gas transport properties of membranes based on P84 polyimideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Yi Shen Abstract P84 polyimide membranes with thicknesses ranging from 6 to 310 ,m were successfully fabricated by spin coating. The glass transition temperature of the P84 powder was found to be 315°C using differential scanning calorimetry, whereas its decomposition temperature was 536°C using thermogravimetric analysis. Scanning electron microscopy was used to examine the morphology of the membranes. The permeability of single gas (He, N2, O2, and CO2) and the ideal selectivity of gas pair (O2/N2, He/CO2, CO2/N2, and He/O2), as a function of membrane thickness, were determined. The results showed that the permeability of a single gas increased with increasing membrane thickness, whereas the selectivity of a given gas pair was nearly independent of the membrane thickness. The average selectivity of O2/N2, He/CO2, CO2/N2, and He/O2 were found to be 8.2, 10.0, 12.9, and 15.8, respectively. The effects of heat treatment on the membrane morphology and gas transport properties were investigated for three annealing temperatures, i.e., 80°C, 200°C, and 315°C. The membrane annealed at 315°C was cracked due to the stress sustained either during heating or cooling, thereby resulting in little or no selectivity. The permeabilities of P84-118 membrane (118 ,m thickness) annealed at 80°C were 16.2, 0.196, 1.20, and 2.01 Barrer for He, N2, O2, and CO2, respectively. The permeabilities of P84-118 membrane annealed at 200°C decreased by 9.75%, 47.96%, 25.83%, and 30.85% for He, N2, O2, and CO2, respectively, as compared with those at 80°C, whereas the ideal selectivities increased by 42.65%, 30.52%, 32.85%, and 21.63% for O2/N2, He/CO2, CO2/N2, and He/O2, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of surface modifying macromolecules stoichiometric ratio on composite hydrophobic/hydrophilic membranes characteristics and performance in direct contact membrane distillationAICHE JOURNAL, Issue 12 2009M. Qtaishat Abstract The stoichiometric ratio for the synthesis components of hydrophobic new surface modifying macromolecules (nSMM) was altered systematically to produce three different types of nSMMs, which are called hereafter nSMM1, nSMM2, and nSMM3. The newly synthesized SMMs were characterized for fluorine content, average molecular weight, and glass transition temperature. The results showed that fluorine content decreased with increasing the ratio of ,,,-aminopropyl poly(dimethyl siloxane) to 4,4,-methylene bis(phenyl isocyanate). The synthesized nSMMs were blended into hydrophilic polyetherimide (PEI) host polymer to form porous hydrophobic/hydrophilic composite membranes by the phase inversion method. The prepared membranes were characterized by the contact angle measurement, X-ray photoelectron spectroscopy, gas permeation test, measurement of liquid entry pressure of water, and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation and the results were compared with those of commercial polytetraflouroethylene membrane. The effects of the nSMM type on the membrane morphology were identified, which enabled us to link the membrane morphology to the membrane performance. It was found that the nSMM2/PEI membrane yielded the best performance among the tested membranes. In particular, it should be emphasized that the above membrane was superior to the commercial one. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Ultrastructure of activated mouse platelets: A qualitative scanning electron microscopy studyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2008E. Pretorius Abstract Platelets form an integral part of the coagulation process, and their ultrastructure can provide valuable information regarding diseases associated with hemostasis. During coagulation, platelets aggregate; this aggregation can be achieved in vitro, by adding thrombin to platelet-rich plasma. Previous research showed that human thrombin could be used successfully to activate mouse platelets. When conservative changes are included, the amino acid similarity between human and mouse thrombin is ,75%. In this qualitative study, we compare the ultrastructure of mouse platelet aggregates activated by human thrombin as well as two concentrations of mouse thrombin, using the scanning electron microscope. Results show that both human and mouse thrombin activate platelets to form aggregates with typical pseudopodia formation. Magnification up to 250,000× showed membrane morphology with the open canalicular system pores visible in both the mouse- and human-activated platelets. It is therefore concluded that mouse platelets can be successfully aggregated using either mouse or human thrombin. Microsc. Res. Tech. 2008. © 2008 Wiley-Liss, Inc. [source] Progesterone induces activation in Octopus vulgaris spermatozoaMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 1 2001Elisabetta Tosti Abstract The purpose of the present study was to determine whether Octopus vulgaris spermatozoa are activated by progesterone stimulation. Spermatozoa were collected from the spermatophores in the Needham's sac of the male (MS) and from the spermathecae of oviducal glands of the female (FS). We used transmission (TEM) and scanning (SEM) electron microscopy to study the morphology of untreated, Ca2+ ionophore A23187 and progesterone‐treated MS spermatozoa, and untreated FS spermatozoa. We showed that ionophore and progesterone stimulation of MS spermatozoa induce breakdown of the membranes overlapping the acrosomal region, exposing the spiralized acrosome. These modifications resemble the acrosome reaction observed in other species. FS stored in the spermathecae did not show the membranes covering the acrosomal region present in the MS spermatozoa. When ionophore and progesterone treatments were performed in Ca2+‐free artificial sea water, no changes were observed, suggesting the role of external calcium in modifying membrane morphology. Lectin studies showed a different fluorescence distribution and membrane arrangement of FS‐untreated spermatozoa with respect to the MS, suggesting that spermatozoa transferred in the female genital tract after mating, are stored in a pre‐activated state. The plasma membrane of the untreated MS and FS spermatozoa was labelled with Progesterone‐BSA‐FITC, indicating the presence of plasma membrane progesterone receptor. Taken together these data suggest that progesterone induces an acrosome‐ like reaction in MS spermatozoa similar to that induced by calcium elevation. In addition progesterone may play a role in the pre‐activation of spermatozoa stored in the female tract, further supporting the hypothesized parallelism between cephalopods and vertebrates. Mol. Reprod. Dev. 59:97–105, 2001. © 2001 Wiley‐Liss, Inc. [source] Synthesis of mesoporous alumina,titania membranes by the sol-gel methodASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010A. Bottino Abstract Ceramic tubular membranes with alumina,titania top layers were prepared using the dipping procedure and a mixed sol composed of both boehmite and titania. The influence of the Ti/Al ratio, the amount of an organic additive (namely hydroxypropylcellulose), the dip-time, the number of depositions and drying,calcination conditions on the membrane morphology and transport properties were investigated. The conditions for the formation of a defect-free and homogeneous top layer were individuated. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Reversible Control of Exo - and Endo -Budding Transitions in a Photosensitive Lipid MembraneCHEMBIOCHEM, Issue 2 2009Ken-ichi Ishii Abstract We have developed a method for the photomanipulation of lipid membrane morphology in which the shape of a vesicle can be switched by light through the use of a synthetic photosensitive amphiphile containing an azobenzene unit (KAON12). We prepared cell-sized liposomes from KAON12 and 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC) and conducted real-time observations of vesicular transformation in the photosensitive liposome by phase-contrast microscopy. Budding transitions,either budding toward the centre of the liposome (endo -bud) or budding out of the liposome (exo- bud),could be controlled by light. We discuss the mechanism of this transformation in terms of the change in the effective membrane surface area due to photoisomerization of the constituent molecules. [source] | ||||||||||