Growth-dependent Surface Characteristics of Hansenula polymorpha: Implications for Expanded Bed Adsorption Chromatography

Nadia Naz,Roy N. Dsouza,Vikas Yelemane,Rami Reddy Vennapusa,Martin Kangwa,Marcelo Fernández-Lahore 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.3

The cell surface characteristics of a methylotrophic wild-type strain of yeast, Hansenula polymorpha, was investigated at different growth stages (early log, late log, stationary and death) of the biomass under different conditions (low and high salt in intact and disrupted forms) using extended DLVO theory. Biomass was characterized by contact angle measurements as well as zeta potential determinations. These measurements were used to describe the hydrophobic, polar, and electrostatic behavior of the biomass in its growth stages. Consequently, interaction free energy vs. distance profiles of the biomass with anionexchange and HIC adsorbents were conveniently generated. A strong interaction was calculated between cells and the adsorbents in the stationary and death phases of the biomass illustrated by the striking correlation between theoretical predictions and biomass deposition experiments. The physico-chemical properties of biomass in different growth phases have important implications for expanded bed adsorption chromatography, where unfavorable biomassadsorbent interactions adversely affect process efficiency.

Adhesion mechanism of bisphenol A diglycidyl ether (BADGE) on an α-Fe₂O₃ (0001) surface

Lee, J.H.,Choe, Y.,Lee, S.G. Korean Society of Industrial and Engineering Chemi 2017 Journal of industrial and engineering chemistry Vol.53 No.-

We investigated the adhesion behavior and electronic properties of an epoxy adhesive on an α-Fe<SUB>2</SUB>O<SUB>3</SUB> (0001) surface using density functional theory (DFT). We found the significant attractive interactions including cation-π interactions between the aromatic rings and the Fe<SUB>2</SUB>O<SUB>3</SUB> surface, and the electrostatic interactions between the O atom of the hydroxyl group and the Fe atoms of the Fe<SUB>2</SUB>O<SUB>3</SUB> surface. Upon adsorption of the epoxy adhesive, local density of states (LDOS) analysis reveals an overall broadening of peaks as well as band gap narrowing, indicating that changes to the electronic properties of the surface occur along with charge transfer.

Adhesion mechanism of bisphenol A diglycidyl ether (BADGE) on an α-Fe2O3 (0001) surface

이지혜,최영선,이승걸 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

We investigated the adhesion behavior and electronic properties of an epoxy adhesive on an a-Fe2O3 (0001) surface using density functional theory (DFT). We found the significant attractive interactions including cation–p interactions between the aromatic rings and the Fe2O3 surface, and the electrostatic interactions between the O atom of the hydroxyl group and the Fe atoms of the Fe2O3 surface. Upon adsorption of the epoxy adhesive, local density of states (LDOS) analysis reveals an overall broadening of peaks as well as band gap narrowing, indicating that changes to the electronic properties of the surface occur along with charge transfer.

Extended JKR theory on adhesive contact between elastic coatings on rigid cylinders under plane strain

Sohn, D.,Won, H.S.,Jang, B.,Kim, J.H.,Lee, H.J.,Choi, S.T. Pergamon Press ; Elsevier Science Ltd 2015 International journal of solids and structures Vol.71 No.-

This study extended the conventional JKR theory on adhesive contact between elastic cylinders to the frictionless adhesive contact between elastic films coated on rigid cylindrical rollers. The plane-strain elasticity problem of indentation on an elastic film perfectly bonded to a rigid half-plane was revisited, with which the force-depth relations for both flat and cylindrical indentations were obtained in a simple form. By following Hertz analysis and using the solution of the cylindrical indentation on an elastic film, the adhesionless Hertzian contact between elastic films coated on rigid cylinders was obtained. However, the obtained Hertzian contact state should be considered as an approximate solution, since the pressure distributions in the contact region of the two elastic films may not match perfectly each other in the case of different Poisson's ratios or thicknesses of the elastic films. By properly superposing the linear elastic solutions of flat and cylindrical indentations, the approximate solution to the adhesive JKR contact state between elastic films coated on rigid cylinders was also obtained, of which the relations between applied force, penetration depth, and contact width were expressed in terms of the geometric parameters and elastic constants of the two elastic films. The pull-off force at the moment of debonding two elastic films was also obtained as a function of the adhesion energy and compared with the normal two-dimensional JKR result.

Effect of specific functional groups on oil adhesion from mica substrate: Implications for low salinity effect

Jiazhong Wu,Fanghui Liu,Hui Yang,Shijing Xu,Quan Xie,Minghui Zhang,TING CHEN,Guangxin Hu,Jinben Wang 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.56 No.-

Low salinity effect has been in the center of attention as a cost-effective and environmentally friendlytechnique. Wettability alteration of the oil/brine/mica system appears to be the identified mechanism(s)to trigger the low salinity effect. While the effect of water chemistry and minerology on the wettability ofthe system has been extensively investigated, few studies have investigated the effect of specific functiongroups from crude oil on the system wettability, limiting the understanding of how specific functionalgroup contributes to the wettability. We thus experimentally measured the adhesion forces betweenmica surfaces and functional groups (e.g., C6H5–, CH3–, COOH–, and NH2–) in the presence of differentaqueous ionic solutions using chemical force microscopy (CFM). Moreover, to understand thecontribution of the structural force, the traditional Derjaguin–Landau–Verwey–Overbeek (DLVO) theorywas extended (denoted as EDLVO) tofit the force profiles using a Gauss model. Our results showed thatthe adhesion force between mica and functional groups in a decreasing order was –NH2> –COOH> –CH3> –C6H5. We also found that while DLVO forces strongly affected the tip-surface contact due to theinteractions among oil/brine/mica interfaces, the structural forces also played an important role in adistance of 1–20 nm due to the presence of H-bonds between COOH-terminated or NH2-terminated tipand mica surface. We therefore conclude that the structural force largely contributes to the adhesionforce due to the hydrophilicity or polarity of functional groups, and nucleophilic property (such as phenylgroup). Our results suggest that the polarity of the crude oil needs to be considered to screen a candidatereservoir for low salinity waterflooding projects.

Interaction forces between spores and planar surfaces in aqueous solutions

Chung, E.,Yiacoumi, S.,Tsouris, C. Elsevier 2014 Colloids and surfaces. A, Physicochemical and engi Vol.443 No.-

Bacterial spore interactions with planar surfaces in aquatic environments, including adhesive forces and force-distance profiles, are influenced by the geometry and physicochemical properties of the system. The characteristics of spores of Bacillus thuringiensis (Bt) are determined using electron microscopy and electrokinetic measurements. The average size of the spores is 1.57μm long and 0.86μm wide, and the zeta potential values are negative for the solutions used in this work. The zeta potentials of the spores and mica surfaces used in the experiments are measured as a function of pH and ionic strength. The Derjaguin, Landau, Verwey and Overbeek (DLVO) theory is employed to predict the interaction force between the spores and planar surfaces as a function of the separation distance, and a force balance is used to explain the adhesive force. Theoretical estimations are compared to experimental measurements obtained from atomic force microscopy (AFM). The DLVO-based calculations are consistent with AFM force measurements, while the calculated adhesive force shows some deviations from the measurements. The deviations can be minimized by considering the roughness of the Bt spore and substrate surfaces. Results are important in the understanding of spore interactions with environmental surfaces in aquatic systems.

Characterization of elastic modulus and work of adhesion in elastomeric polymers using microinstrumented indentation technique

Lee, G.,Kang, S.K.,Kwon, D. Elsevier Sequoia 2008 Materials science & engineering. properties, micro Vol.496 No.1

This study combines Johnson-Kendall-Roberts (JKR) theory with the instrumented indentation technique (IIT) to evaluate the work of adhesion and modulus of elastomeric polymers. Indentation testing was used to obtain load-displacement data for contact between a tungsten carbide indenter and the elastomeric polymer. The JKR contact model, which was designed to take polymer viscoelastic effects into account, was applied to adjust the contact area and the elastic modulus, which the Hertzian contact model would respectively underestimate and overestimate. In addition, we obtained the thermodynamic work of adhesion by considering the surface energy in this contact model. In order to define the relation between the JKR contact radius and applied load without measuring the contact radius optically, we used a relation between applied load and contact stiffness by examining the correlation between the JKR contact radius and stiffness through dimensional analysis with 14 elastomeric polymers. This work demonstrated that the interfacial work of adhesion and elastic modulus of a compliant polymer can be obtained from simple instrumented indentation testing without area measurement, and provided an algorithm for compliant polymer characterization.

約款規制法·消費者法의 民法에의 統合問題에 대한 管見

이준형(Lee, Joon-Hyong) 한국재산법학회 2009 재산법연구 Vol.26 No.2

The integration of consumer protection laws, including the Standardized Contract Terms Regulating Act, into the Civil Code belongs to one of the hottest potatoes in the current discourses for preparations of the new draft of the revised Korean Civil Code, in the forms of such questions as: "Is it necessary, and how much?" This article will scrutinize the integration problem from the comparative perspective, with the special focus on the implications from the French experiences. Tracing all the discussions from Saleilles' adhesion contract theory(1901) through enactment of the Consumption Code(1993) to the newly publicized Contract Code draft by the French Ministry of Justice(2008), the author could infer some lessons as follow: Firstly, consumer protection law is a kind of newcomer in comparison with law of contract, but that has played and will play so important a role in the practical and theoretical developments of this, that we should improve the current situation of almost completely disconnected relationship between them. Secondly, though law of contract and consumer protection law shares much each other, it should be admitted that they differ in purposes or ideas, as well as legislative techniques. Thirdly, there are urgent preparations to be taken right now: to establish minimal clauses on principles of consumer law within the civil code, and to build up the legal system of consumer (private) law, including the out-of-dated Standardized Contract Terms Regulating Act, for now as well as for the future.

후판 단일 겹침 접착 조인트의 파손강도에 관한 연구

박재현(Jae-Hyun Park),최진호(Jin-Ho Choi),권진회(Jin-Hwe Kweon) 한국항공우주학회 2010 韓國航空宇宙學會誌 Vol.38 No.2

복합재료 구조물에서 조인트 부위는 매우 취약한 부분이다. 본 논문에서는 후판 알루미늄-알루미늄 조인트 및 복합재-알루미늄 조인트를 접착제로 접합하여 제작한 다음, 인장실험을 수행하여 파손형태를 고찰하였다. 또한, 항복 변형률에 기초한 수정 파손영역 이론을 제안하였으며, 파괴모드별 파손하중과 상호 비교하였다. 후판 알루미늄-알루미늄 조인트와 복합재-알루미늄 조인트의 파손강도를 동일한 파손기준값을 적용하여 예측하였으며, 제작된 14종류의 시편에서는 최대 19.3% 오차범위 내에서 파손강도를 예측할 수 있었다. The joints are often the weakest areas in composite structures. In this paper, the thick aluminum-aluminum joint specimens and thick composite-aluminum single lap adhesive joint specimens were manufactured and the tensile tests were performed. The fracture mode of each specimen was investigated and the modified damage zone theory based on the yield strain was proposed and compared with experimental failure load of each mode. The failure loads of the thick aluminum-aluminum joint and composite-aluminum joint were predicted by the same failure criterion and they could be predicted to within 19.3% using the damage zone ratio method for all 14 cases investigated.

Experimental Study on the Fatigue Crack Propagation Behavior of DCB Specimen with Aluminum Foam

한문식,조재웅,최해규,조종두 한국정밀공학회 2013 International Journal of Precision Engineering and Vol.14 No.8

Adhesive processing is increasingly used with bonding method for joined structures. Gathering fracture toughness data regarding the bonded joint is essential to render bonded structures safe. However, researches centering on the strength evaluation of bonding joints for bonded structures of aluminum foam, which has excellent mechanical properties like light weight and impact absorption, are lacking. In this study, DCB test specimen built of aluminum foam is fabricated by the British Standard (BS) and the International Standard Organization (ISO) guidelines. Fatigue test is performed with mode I for DCB test specimen. The fatigue test results with the four types of test specimens with beam heights as parameters show progressed crack within a few cycles as beam height increases. Meanwhile, the energy release rate per crack length becomes higher as the beam height decreases. The fracture behavior of actual composite material bonded by aluminum foam can be analyzed through the correlation of results obtained by tests. The mechanical properties of actual composite structure can be understood by utilizing the bonded aluminum foam.