Mesoscopic coarse‐grained simulations of hydrophobic charge induction chromatography (HCIC) for protein purification

Mesoscopic coarse‐grained simulations are adopted to investigate interfacial mechanisms of hydrophobic charged induction chromatography for protein purification by regulating pH. Simulations results indicate that: (i) lysozyme can be adsorbed mainly with “top end‐on” and “bottom end‐on” orientation on hydrophobic surfaces, dominated by the two hydrophobic regions located at both ends of lysozyme's long axis. Elution from the “top end‐on” orientation is more difficult than that from the “bottom end‐on” orientation; (ii) a higher ligand density can get a faster adsorption rate and stronger adsorption. Interestingly, the effect of ligand density on the desorption is mainly determined by the distribution probability of the positively charged groups of ligands; (iii) a higher ionic strength can lead to a wider orientation distribution, a stronger adsorption and a lower elution rate. This work might provide an efficient way to optimize the operating conditions and designing novel ligands. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2035–2047, 2015     

Phenomenological and mathematical analysis of the orientation in biaxially drawn polymeric films

Equations are derived that relate the orientation of “pseudo-affine” reoriented structural units after a biaxial deformation to the degrees and the directions of the effective drawings. The connection between these drawing parameters and those externally applied is analyzed in detail. It is shown how a comparison of these two sets of drawing parameters allows conclusions regarding the distribution throughout the material of the stresses that cause the deformation, the inhomogeneity of the deformation, and the role of non-orienting flow during deformation. In particular, the orientation of biaxially drawn poly(ethylene terephthalate) films is investigated, and it is shown what general information can be obtained on the deformation behavior of this material on the basis of these considerations.     

Interrogation of “surface,” “skin,” and “core” orientation in thermotropic liquid‐crystalline copolyester moldings by near‐edge X‐ray absorption fine structure and wide‐angle X‐ray scattering

Injection molding thermotropic liquid‐crystalline polymers (TLCPs) usually results in the fabrication of molded articles that possess complex states of orientation that vary greatly as a function of thickness. “Skin‐core” morphologies are often observed in TLCP moldings. Given that both “core” and “skin” orientation states may often differ both in magnitude and direction, deconvolution of these complex orientation states requires a method to separately characterize molecular orientation in the surface region. A combination of two‐dimensional wide‐angle X‐ray scattering (WAXS) in transmission and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy is used to probe the molecular orientation in injection molded plaques fabricated from a 4,4′‐dihydroxy‐α‐methylstilbene (DHαMS)‐based thermotropic liquid crystalline copolyester. Partial electron yield (PEY) mode NEXAFS is a noninvasive ex situ characterization tool with exquisite surface sensitivity that samples to a depth of 2 nm. The effects of plaque geometry and injection molding processing conditions on surface orientation in the regions on‐ and off‐ axis to the centerline of injection molded plaques are presented and discussed. Quantitative comparisons are made between orientation parameters obtained by NEXAFS and those from 2D WAXS in transmission, which are dominated by the microstructure in the skin and core regions. Some qualitative comparisons are also made with 2D WAXS results from the literature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Anisotropic shrinkage of injection-molded rubber

The anisotropic characteristics of injection-molded flat rubber sheets were investigated. The shrinkage and mechanical properties were measured in two directions: parallel and perpendicular to the flow direction. The results showed that (1) the shrinkage in the parallel direction is larger than that in the perpendicular direction, (2) such anisotropic shrinkage increases with the increase of vulcanization temperature and flow distance, (3) similar anisotropy was also noticed in 300% modulus, tensile strength, and elongation. Two kinds of orientation, “shear orientation” and “expanded orientation,” were observed. The former occurs by plug flow, and the latter by the expansion of the materials. The shrinkage was independent of the expanded orientation but was strongly associated with the shear orientation, while the mechanical properties were affected by the expanded orientation.     

新时代高职院校学生思想政治工作现状调查——以唐山工业职业技术学院为例

高职院校担当立德树人的根本任务,必须加强学生思想政治教育工作。通过问卷调查,从政治取向、培育践行社会主义核心价值观、心理健康、道德品质、法治观念等多各方面对高职院校学生思想政治状况进行了调查,发现高职学生思想政治状况良好,高职院校学生思政工作的问题主要集中在“思想政治项目”“课程思政改革”和“学生人生规划”等方面。针对问题,结合党的最新理论政策要求,从“加快构建高职院校思想政治工作体系”“加大高职院校思想政治教育项目供给侧结构性改革力度”“充分发挥学生主体作用”等方面提出对策和建议。     

Mechanische eigenschaften von polyesterfasern bei kurzzeitiger zugbeanspruchung, 4. Strukturveränderungen durch kurzzeitverformung an polyester-monofilamentgarn

Interferometric measurements of a PETP-monofilament yarn show that the orientation of the high pre-orientated material decreases after stretching and relaxing. The effect of desorientation is more distinctive by a slower deformation then by a high-speed deformation. The lower decrease is caused by a slower deformation. Material strained with a rate of 10⁴%/s shows “crazes” visible by interferometry. These “crazes” are not cracks but sites with lowered orientation. For slower deformation it is visible interferometrically that the orientation of the macromolecules in the fiber is asymmetric. DTA-curves from PETP-fibres show an exothermic peak between 30 and 80°C which can be related to specific structures of the non cristalline regions. By low-speed straining this peak shifts to lower temperatures. Stress-free storing of the material causes the peak to move back to the original temperature. For material deformated at high-speeds this peak does not change its position.     

Biaxial deformation of polyamide‐6: Assessment of orientation by means of infrared trichroism

Infrared spectroscopy was used to study the evolution of structure in films of polyamide‐6 drawn on a Cellier tenter frame laboratory tester under conditions of simultaneous equibiaxial stretching and planar uniaxial stretching. The “tilted film” method was used to obtain trichroic spectra corresponding to the machine, transverse, and normal directions, as well the “structural factor” spectrum. From these it was possible to obtain information on the molecular orientation and the evolution of the crystalline structure. The starting films, prepared by melt casting from an extruder on a chilled roll, contained predominantly the mesomorphic β form. The structural factor spectra confirmed that strain‐induced transformation into the α form occurred upon drawing, and that the amount of α form increased with the extent of drawing. The trichroic spectra showed that the molecular orientation was localized mainly, but not exclusively, in the α form. Orientation functions could be determined for both the molecular chain axis and the normal to the hydrogen‐bonded sheets. For both the equibiaxial and planar uniaxial films, these sheets were found to be strongly oriented parallel to the plane of the film, with the degree of orientation increasing with overall draw ratio. For the biaxial samples, the molecular chain orientation was found to be equibiaxial, as expected. Mechanical test results indicated that the chains are evenly distributed in the film plane rather than showing a preference for the two orthogonal draw directions. For the planar uniaxial samples, the chain orientation was predominantly in the draw direction, but some degree of orientation in the transverse direction was also observed. The variation of orientation functions with draw ratio suggested that the α structure evolves in two stages, the first involving chain orientation in the draw direction and the second involving rotation of the sheets into the plane of the film.     

Control of molecular orientation

I. Amorphous polymers . The mechanical performance of a glassy amorphous polymer is strongly dependent upon molecular orientation. The pattern of molecular orientation is governed by the kinematics (and temperature) of mechanical forming operations. Three types of controllable orientation are: (a) uniaxial, (b) biaxial, and (c) “crossed.” The optimum pattern of orientation in a part is one which is appropriate for the mechanical stresses encountered in service. For a fiber subjected to tensile and bending loads, uniaxial orientation is appropriate. A shell structure, subjected to multiaxial stresses, requires either biaxial or crossed orientation for maximum performance. As a rule, the maximum achievable multidirectional strength in such a structure is less than the maximum strength of a uniaxially oriented fiber. II. Crystalline polymers . Oriented crystalline polymer structures can be created in two distinct ways. An isotropic polycrystalline polymer can be deformed below the melting point, with extensive reorganization of the crystal morphology, or an oriented amorphous melt can undergo crystallization to yield oriented crystalline polymer. Performance of an oriented semicrystalline polymer depends upon orientation of the amorphous portion as well as orientation of the crystallites. As with amorphous polymers, orientation can be uniaxial, biaxial, or crossed. “Orientation” usually denotes c-axis orientation only, but drawing followed by rolling can result in double orientation—orientation of a-axis, b-axis, and c-axis.     

Investigation of local orientation and stress analysis of PZT-based materials using micro-probe polarized Raman spectroscopy

Investigation of crystallographic orientation and the related residual stress fields stored in piezoelectric sensor/actuator devices would improve reliability of industrial products and help to optimize the entire production process. Micro-probe Raman piezospectroscopy is a very attractive technique, yet not applied to lead zirconate titanate (PZT)-based materials, as the response is convoluted into contributions arising not only from stress, but also from crystallographic orientation. In this work, we have attempted to evaluate the correlation between Raman spectra and orientation in two differently doped lead zirconate titanate materials (PZT–LN and PZT–NSY), finding in the “softer” PZT a correlation between crystal orientation and Raman shift. We performed also some calibration experiments, and a piezospectroscopic (PS) coefficient has been retrieved in the “harder” PZT.     

Modulus development in oriented short-glass-fiber-reinforced polymer composites

The increase in modulus obtained in a short-glass-fiber-reinforced polymer composite as a result of uniaxial deformation may be related to the observed increase in both fiber and matrix orientation. Quantitative measurements of both fiber and matrix orientation are presented for a series of samples of short-glass-fiber-reinforced polyoxymethylene copolymer, processed to various substantial deformation ratios by solid-phase hydrostatic extrusion. The polymer matrix becomes highly oriented at modest deformations, but the glass fibers orient in a slower pseudo-affine manner and dominate the development of modulus in the composite. A simple “law-of-mixtures” model is used to demonstrate that perfect uniaxial orientation of the fibers is not achieved, but a better fit to measured modulus data is obtained by using an “aggregate” model applied to oriented fibers in an oriented matrix. The development of modulus with deformation ratio may be predicted very well if it is assumed that:

• the composite consists of a series-coupled array of sub-units, each containing continuous and fully oriented fibers in a fully oriented matrix; and
• orientation of the sub-units develops with deformation in a pseudo-affine manner.

     

SPH simulation of oil displacement in cavity-fracture structures

This paper presents a study of the immiscible displacement of oil by water in cavity-fracture structures using smoothed particle hydrodynamics (SPH). The surface tension and wetting behavior are incorporated into the equation of motion, and pseudo periodic boundary conditions are applied. As for “middle-fractured” structure, it is found that the ultimate oil recovery is almost determined by the height of fracture regardless of its orientation, and the result compares well with corresponding experiments. Besides, the water-wet wall is favorable to higher oil recovery. A systematic exploration is carried out on “upper-fractured” structure for the feasibility of gravity drainage, where a critical width of fracture is found, beyond which the oil in the cavity can be driven out. The possible development of SPH in this background for large-scale simulation is prospected finally.     

Dissipative particle dynamics studies on the interfacial tension of A/B homopolymer blends and the effect of Janus nanorods

Janus nanorods are used as a novel rigid compatibilizer to improve the interfacial tension of incompatible A/B homopolymer blends. Dissipative particle dynamics (DPD) methods are preformed to explore the effect of Janus nanorods on the interfacial tension. The results show that Janus nanorods are a good compatibilizer only when the appropriate length is chosen, which is different from the traditional coil compatibilizer (surfactants and block copolymers). The length of the Janus nanorods can significantly influence their orientation through the competition between the entropic and enthalpic effects. The shorter Janus nanorods preferring “standing” have a better efficiency in improving the interfacial tension than the longer ones preferring “lying.” If we can control the orientation of the longer Janus nanorods, they are still a good compatibilizer. This simulation work can widen the application of Janus nanoparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44098.     

Electron spin resonance and the structure of carbon fibers

The ESR properties of 3000°C heat treated fibers derived from mesophase pitch and PAN have been measured and compared with computer-simulated spectra. Conduction electron motional averaging was observed in the PAN- and pitch-based fibers with domains small in the transverse direction. When perpendicular to the applied field, pitch-based fibers with large transverse domains exhibited a complex spectrum indicating no motional averaging by the conduction electrons. Computer-simulated spectra were in agreement with experiment and were useful in the determination of “single crystallite” ESR parameters. The relationship between ESR behavior and fiber structure is discussed.     

Viscoelastic study of ionomers

Stress-relaxation curves were obtained for ionomers containing different cations, per cents of ionization, and thermal treatments. Differences in the rheological behavior were found to depend more on the ionization level than on the ion. A recently proposed model for ionomers is discussed and found to be consistent with these results. In terms of this model the degree of ionization in the polymer acts as a regulator for the growth of small oriented lamellar (crystalline) regions. In the most general terms, the mechanical behavior and strength of ionomers appears dominated by the existence of “hard” regions interspersed among “soft” regions. In the polymers studied here there was some slight crystallinity; however, similar effects and explanations are probably suitable for amorphous “ionomers.” Toughness was also found in some completely amorphous carboxylcontaining copolymers without added ionic salts. The same explanation of “hard” regions interspersed among soft regions is also valid here. The “blocky” nature of the copolymerization may play a role in setting up this type of structure.     

Molecular orientation distributions during injection molding of liquid crystalline polymers: Ex situ investigation of partially filled moldings

The development of molecular orientation in thermotropic liquid crystalline polymers (TLCPs) during injection molding has been investigated using two‐dimensional wide‐angle X‐ray scattering coordinated with numerical computations employing the Larson–Doi polydomain model. Orientation distributions were measured in “short shot” moldings to characterize structural evolution prior to completion of mold filling, in both thin and thick rectangular plaques. Distinct orientation patterns are observed near the filling front. In particular, strong extension at the melt front results in nearly transverse molecular alignment. Far away from the flow front shear competes with extension to produce complex spatial distributions of orientation. The relative influence of shear is stronger in the thin plaque, producing orientation along the filling direction. Exploiting an analogy between the Larson–Doi model and a fiber orientation model, we test the ability of process simulation tools to predict TLCP orientation distributions during molding. Substantial discrepancies between model predictions and experimental measurements are found near the flow front in partially filled short shots, attributed to the limits of the Hele–Shaw approximation used in the computations. Much of the flow front effect is however “washed out” by subsequent shear flow as mold filling progresses, leading to improved agreement between experiment and corresponding numerical predictions. POLYM. ENG. SCI.,, 2011. © 2011 Society of Plastics Engineers     

The energy balance in modeling gas-phase chemical reactor dynamics

Enthalpy cannot be stored. In spite of this fact it is frequently assumed in analysis of chemical reactor dynamics that the energy balance can be replaced by an “enthalpy balance”, which actually implies that enthalpy would be stored. No investigation of the errors introduced by this assumption has been found in the literature.In this paper the errors obtained when using an “enthalpy balance” in modeling gas-phase reactor dynamics are studied. After formulating the general energy balance as well as its linearized version for gas phase CSTR-reactors a computation of the local stability of two simple exothermic reaction systems quantitatively illustrates the inaccuracy of the “enthalpy balance” formulation.In the examples treated, the use of an “enthalpy balance” results in nonconservative design for stability. Further, it gives results which numerically are considerably in error and it predicts another type of behavior than the energy balance does (nonoscillatory compared to oscillatory behavior).Since there are no methods available to estimate the size of the errors, and since the energy balance is not more difficult to use than the “enthalpy balance” is, the latter concept could without loss be buried once and for all.     

Order-disorder transitions in the extrusion of fiber-filled poly (ethylene terephthalate) and blends

Order-disorder transitions occur in fiber orientation and distribution during extrusion of fiber-filled poly (ethylene terephthalate) and its blends with other polymers. Associated with these transitions are three characteristic regimes of extrudate surface morphology, cross-sectional structure and fiber distribution. Low wall shear rates result in a “smooth porcupine” surface, polygonal cross section, and uniform fiber distribution. Medium wall shear rates produce a “rough porcupine” surface, irregular cross section and tubular depletive fiber distribution with fibers depleting at a relative radial position r/R of 0.63 and accumulating at the surface and the axis. This is exactly opposite to the tubular pinch effect observed for neutrally buoyant rigid spheres which accumulate at r/R of 0.63 and deplete at the surface and the axis. High wall shear rates give a “shorn porcupine” surface, rounded or distorted polygonal cross section and radial migration of fibers toward the axis. The extant of disorder decreases with increasing pseudoplasticity, of the fluid, suggesting that the characteristic fiber orientation, distribution and transitions arise from normal stress effect and/or the eccentric rotation of fibers dictated by the complex velocity profile of the flowing fluid. These phenomena have not been previously reported.     

Transverse orientation dies for solid-state extrusion of polymers. Part II: Orientation and properties of extrudates

Biaxial orientation in polymer products is normally brought about by the application of planar tensile stresses to sheets or films in either the “plastic” or “rubbery” state. More recently, other techniques have been explored as, for instance, the superimposition of rotational components in planes perpendicular to compressive forces. The present work is concerned with the solid-state extrusion of very high molecular mass crystalline polymers, such as poly(tetra)fluoroethylene (PTFE) and ultrahigh-molecular-weight polyethylene (UHMWPE), using dies featuring converging and diverging walls perpendicular, to each other and with a cross-section area at the entry being the same as at the exit. Measurements of birefringence and tensile strength on solid section extrudates have shown that dies with small converging angles, known as fish tail dies, produce a uniaxial type of orientation along the transverse direction, while dies with large converging angles at the entry region give rise to an unbalanced biaxial orientation.     

Orientation distribution in the noncrystalline regions of biaxially drawn poly(ethylene terephthalate) film: A chain-intrinsic fluorescence study

We have studied development of the in-plane distribution of “amorphous orientation” during sequential and simultaneous biaxial drawing of poly(ethylene terephthalate) film, using polarized intrinsic fluorescence. The machine direction (MD) draw ratio was always fixed at 3.5, and the transverse direction (TD) draw ratio was varied. The rate of increase in the proportion of TD-oriented chains with increasing TD draw ratio is almost identical in the sequential and simultaneous processes up to a draw ratio of 2.7. At this point, sequential drawing starts to involve transverse realignment of MD-oriented chains, which accelerates redistribution of orientation from the MD to the TD. Consequently, in sequential drawing, a “balanced” biaxial orientation distribution is achieved at a TD draw ratio significantly below the MD draw ratio, whereas at the same TD draw ratio in the simultaneous process, MD orientation remains dominant. At equal MD and TD draw ratios, the non-crystalline chains in sequentially drawn film are predominantly oriented along the TD, but their orientation distribution is isotropic in simultaneously drawn film. High-temperature annealing at fixed dimensions diminishes the proportion of TD-oriented chains in films with transverse draw ratios < 2.5. We attribute this to a more highly developed crystallite network in the MD, which constrains orientational relaxation along the MD. A balanced distribution of amorphous orientation is directly responsible for achieving balanced tensile strength and balanced extensibility. © 1993 John Wiley & Sons, Inc.     

Zur lebensmittelrechtlichen Beurteilung hervorhebender Hinweise bei Fetten und fetthaltigen Zubereitungen

Legal Food Estimation of Remarks Concerning the Quality of Fats and Fat Containing Preparations For legal food estimation of commercial fats and oils as well as of preparations, industrially produced of fats and oils, the general regulations of the food and requisite law of 15. 8. 1974 in context with definitions e. g. in the rules of the German foodbook or in guiding principles of the food management are to notice concerning accentuating quality hints as “fine”, “first class”, “good”, “pure”, “natural” or similar. The relations are explained on butter or pure butter fat and butter pastry, on lard, lard pastry, on native and refined sunflower oils as on hardened marine animal oil and preparations produced of these ingredients.