• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.845-851
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• 2008

TolC is an outer membrane porin protein and an essential component of drug efflux and type-I secretion systems in Gram-negative bacteria. TolC comprises a periplasmic $\alpha$-helical barrel domain and a membrane-embedded $\beta$-barrel domain. TdeA, a functional and structural homolog of TolC, is required for toxin and drug export in the pathogenic oral bacterium Actinobacillus actinomycetemcomitans. Here, we report the expression of the periplasmic domain of TdeA as a soluble protein by substitution of the membrane-embedded domain with short linkers, which enabled us to purify the protein in the absence of detergent. We confirmed the structural integrity of the TdeA periplasmic domain by size-exclusion chromatography, circular dichroism spectroscopy, and electron microscopy, which together showed that the periplasmic domain of the TolC protein family fold correctly on its own. We further demonstrated that the periplasmic domain of TdeA interacts with peptidoglycans of the bacterial cell wall, which supports the idea that completely folded TolC family proteins traverse the peptidoglycan layer to interact with inner membrane transporters.

• Bulletin of the Korean Chemical Society
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• v.3 no.1
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• pp.23-30
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• 1982

For the study of transport phenomena of an aqueous NaCl solution through a cuprophane membrane, a new apparatus was constructed. The volumc flow rate Q, the permeability coefficient U, and the permeability constant K were measured or determined by using this apparatus. The experimental temperature range was 5 to $35^{\circ}C$, and the applied pressure increments were 10 to 40 psi. By assuming that the cuprophane membrane is composed of n parallel cylindrical capillaries of circular cross-section and that the flow of the solution through the capillaries follows the Poiseulle law, the mean radius r of the capillaries and the number n of the latter in the membrane were evaluated. By using a reasonable assumption concerning the radius ${\eta}'$ of the species diffusing through the membrane, it was concluded that the contribution of the diffusive flow to the total flow rate Q is less than 10%. Thus, the Q was treated as the rate due to the viscous flow, and the viscosity ${\eta}_m$ of the solution in the membrane phase was evaluted, and it was found that ηm is nearly equal to ${\eta}_b$, the bulk viscosity of the solution. From this fact, it was concluded that in the capillaries, no change occurs in the physical state of the NaCl solution. The value of ( = 4.27 kcal/mole) and ${\Delta}Sm^{\neq}$(4.28 eu) were obtained for the viscous flow. A possible explanation was given.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.1-8
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• 1992

This paper presents a p-version finite element approach for modeling the stress distribution around a circular hole in a finite strip subjected to membrane and flexural behaviors. Also, same problem with a crack emanating from a perforated tension strip was solved by virtual crack extension method. The p-version of the finite element method based on integrals of Legendre polynomials is shown to perform very well for modeling geometries with very steep stress gradients in the vicinity of a circular cutout. Here, the transfinite mapping technique for circular boundaries was used to avoid the discretization errors. The numerical results from the proposed scheme have a good comparison with those by Nisida, Howland, Newman etc. and the conventional finite element approach.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.121-126
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• 2001

Currently, potentiometric method has been employed to measure fuel amount for automobile. However, potentiometer could be malfunctioned or damaged due to the additives or dirt in fuel because a variable electric resistor is immersed in fuel. Therefore, a device employing strain sensor is designed and tested to verify the possibility as an alternative of the conventional fuel sender. Existing fuel tank has irregular cross section. Therefore, buoyancy is not increased linearly as fuel amount is increased. We design a floater that can compensate the irregular cross section of fuel tank and make buoyancy to increase linearly with increasing fuel amount. New fuel sender, comprising of strain gages on circular membrane, the above commented floater and the cover to prevent the disturbance due to sudden acceleration and deceleration, is designed and tested to replace current fuel sender. On the other hand, we are developing strain sensor that has strain gage deposited directly on the circular membrane with cantilever beam.

• Journal of Environmental Science International
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• v.7 no.1
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• pp.62-66
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• 1998

Toxic Mastoparan B(MP-B) which is purified from the venom of the hornet Vespa basalis is a cationic amphlphilic tetradecapeptide. MP-B and Its Ala-substituted analogues were synthesized by solld phase method and the toxic peptide-membrane interactions were examined by circular dichroism(CD) spectra, fluorescence spectra, and leakage abilities in phospholipid membranes. In the presence of phospholipid vesicles, synthetic MP-B and its analogues formed amphiphilic -helical structures, but in the buffer soletion, those exhibited random coil conformation as measured by CD. Fluorescence spectra of MP-B and its analogues which indicated the binding affinity of peptide on phospholipid vesicles showed that the replacement of Lys at position 2 and 11 with Ala caused a remarkable effect in the blue shalt and that at position 2, in the leakage ability of the peptide.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.19-28
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• 2005

The present paper outlines the numerical investigation of the incident wave interactions with fully submerged and floating dual double hull pontoon/vertical porous membrane breakwaters. Two dimensional five fluid-domains hydro-elastic formulation was carried out in the context of linear wave body interaction theory to study the wave interaction with the double hull of pontoon-membranes. The submerged circular pontoon is consisted of double hulls, which is filled with water in the void space between the outer structure and inner solid buoyant structure. Hydrodynamic characteristics of the proposed system with dual floating double-hull-pontoons filled with water have been studied numerically for the various incident waves. This study is a beginning stage research for the dual double hull porous pontoons/vertical porous membranes breakwaters which is ideally designed in order to suppress significantly the transmitted and reflected waves simultaneously.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.69-77
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• 2011

A peristaltic micropump with lightweight piezo-composite actuator (LIPCA) membrane valves is presented. The micropump contained three cylinder chambers that were connected by microchannels and two active membrane valves. A circular miniature LIPCA was developed and manufactured to be used as actuating diaphragms. The LIPCA diaphragm acted as an active membrane valve that alternate between open and closed positions at the inlet and outlet in order to produce high pumping pressure. In this LIPCA, a lead zirconium titanate ceramic with a thickness of 0.1 mm was used as an active layer. The results confirmed that the actuator produced a large out-of-plane deflection. During the design process, a coupled field analysis was conducted in order to predict the actuating behavior of the LIPCA diaphragm; the behavior of the actuator was investigated from both a theoretical and experimental perspective. The active membrane valve concept was introduced as a means for increasing pumping pressure, and microelectromechanical system techniques were used to fabricate the peristaltic micropump. The pumping performance was analyzed experimentally in terms of the flow rate, pumping pressure and power consumption.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.28 no.4
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• pp.290-301
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• 2002

The purpose of this study was to evaluate new bone formation and healing process in rat calvarial bone defects using $BioMesh^{(R)}$. membrane and DFDB. Forty eight rats divided equally into 4 groups of 1 control group and 3 experimental groups. Standardized transosseous circular calvarial defects (8 mm in diameter) were made midparietally. In the control group, the defect was only covered with the soft tissue flap. In the experimental group 1, it was filled with DFDB only, in the experimental group 2, it was covered $BioMesh^{(R)}$. membrane only, and in the experimental group 3, it was filled DFDB and covered with membrane. At the postoperative 1, 2, 4, 8 weeks, rats were sacrificed and histologic and histomorphometric analysis were performed. These results were as follows. In histomorphometric analysis, It showed the greatest amount of new bone formation through experimental in the experimental group 3 (P<0.001). The amount of new bone formation at the central portion of the defect was greater in the experimental group 3 than experimental group 2. $BioMesh^{(R)}$. membrane began to resorb at 1 week and resorbed almost completely at 8 weeks after operation. The collapse of membrane into the defect was observed through the experimental periods in the experimental group 2. In the area of collapsed membrane, new bone formation was restricted. These results suggest that maintenance of some space for new bone to grow is required in the use of $BioMesh^{(R)}$. membrane alone in the defect. It is also thought that use of the membrane may promote new bone growth in DFDB graft.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.882-890
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• 1996

Mechanical properties, including Young's modulus, residual stress and rupture strength, of a thermally evaporated gold film have been measured form a blister test. In a theoretical study, the priniple of minimum potential energy and that of virtual work have been applied to the pressurized circular membrane problem, and load-deflection relations have been derived for typical membrane deflection mode of spheroidal shape. In an experimental study, circular gold membranes of 4800 A-thickness and 3.5mm diameter were fabricated by the silicon electropolishing technique. Mecahnical properties of the thin gold films were deduced from the load-deflection curves obtained by the blister test, Young's moduli, obtianed from blister test, have been in the range of 45-70 GPa, while those of bulk gold have been in the range of 78-80 GPa. Residual stresses in the evaporated gold films have been measured as 28-110MPa in tension, The rupture strength of the gold film has turned out to be almost equal to that of dental gold alloy (310-380MPa). It has been demonstrated that the present specimen fabrication method and blister test apparatus have been effective for simultaneous measurement of Young's modulus, residual stress and repture strength of thin solid films. Especially, the electropolishing technique employed here has provided a simple and practical way to fabricate thin membranes in a circular or an arbitrary shape, which could not be obtained by the conventional anisotropic silicon mecromachining technique.

• Korean Journal of Veterinary Research
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• v.40 no.4
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• pp.691-699
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• 2000

We investigated the effects of nitric oxide (NO) donors, S-nitroso-L-cysteine (Cys-NO) and 3-morpholinosydnonimine hydrochloride (SIN-1), on the contractile and electrical activity of the circular muscle of guinea pig gastric antrum by using intracellular microelectrode technique. The gastric antral circular muscle showed spontaneous phasic contraction and slow wave of membrane potential. Cys-NO ($0.001{\sim}10{\mu}M$) and SIN-1 ($0.001{\sim}100{\mu}M$) reduced not only the tonic and phasic contraction but also the amplitude of slow wave in a concentration dependent manner. NO donors were more potent to inhibit phasic contraction than to do slow wave. These inhibitory effects of NO donors were mimicked by the membrane permeable guanosine-3',5'-cyclic monophosphate (cGMP) analogue, 8-bromo-cyclic GMP (8-br-cGMP, $10{\sim}300{\mu}M$). The inhibitory effects of SIN-1 and Cys-NO were antagonized by the guanylate cyclase inhibitor, 1H[ [1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, $10{\mu}M$). These results suggest that the inhibitory effects of NO donors on the mechanical and electrical activity is mainly mediated by cGMP pathway.