Low-density polyethylene superhydrophobic surface by control of its crystallization behavior

A simple and inexpensive method for forming a low-density polyethylene (LDPE) superhydrophobic surface by controlling the crystallization behavior of LDPE by adjusting the crystallization time and nucleation rate has been proposed. The resulting porous surface, with hierarchical micro- and nanostructures on the beautiful floral designs, has a water contact angle of 173.0degrees +/- 2.5degrees.

Hydrodynamic radius characterization of a vinyl-type polynorbornene by size-exclusion chromatography with a static and dynamic laser light scattering detector

Both absolute molecular weight and molecular sizes (radius of gyration and hydrodynamic radius) of a vinyl-type polynorbornene eluting from size-exclusion chromatography columns were determined by combined with a static and dynamic laser light scattering detector. The hydrodynamic radius of polymer fraction eluting from size-exclusion chromatography columns was obtained from dynamic laser light scattering measurements at only a single angle of 900 by introducing a correction factor. According to the scaling relationship between molecular sizes and molecular weight and the ratio between radius of gyration and hydrodynamic radius, the vinyl-type polynorbornene took a random coil conformation in 1,2,4-trichlorobenzene at 150 degreesC.

Preparation and properties of microporous membrane from poly(vinylidene fluoride-co-tetrafluoroethylene) (F2.4) for membrane distillation

Flat-sheet microporous membranes from F2.4 for membrane distillation (MD) were prepared by phase inversion process. Dimethylacetamide (DMAC) and LiClO(4)(.)3H(2)O/trimethyl phosphate (TMP) were, respectively, used as solvent and pore-forming additives. The effects of casting solution composition, exposure time prior to coagulation and temperature of precipitation bath on F2.4 membrane structure were investigated. The morphology of resultant porous membrane was observed by scanning electron microcopy. Some natures of F2.4 porous membrane after drying in air, such as mechanical properties and hydrophobicity, were exhibited and compared with poly(vinylidene fluoride) (PVDF) membrane prepared by the same ways. Stress-at-break and strength stress of F2.4 microporous membrane are higher than that of PVDF membrane, and elongation percentage of F2.4 membrane at break is about eight-fold as great as that of PVDF membrane. Contact angle of F2.4 microporous membrane to water (86.6 +/- 0.51degrees) was also larger than that of PVDF mernbrane (80.0 +/- 0.78degrees). MD experiment was carried out using a direct contact membrane distillation (DCMD) configuration as final test to permeate performance of resultant microporous membrane.

Preparation and characterization of ordered yttrium arachidate multilayer

The behavior of arachidic acid on the surface of YCI3 aqueous subphase was studied by LB and Brewster angle microscopy techniques. The results showed that the pre-compressing time and the pH of the subphase played an important role in the forming of the monolayer. The monolayer on the subphase surface was irreversible. If the monolayer was compressed into wrinkles, the monolayer could not become uniform again. The optimum transferring conditions were selected and the ordered yttrium arachidate multilayer with a long spacing of 4.96 nm and a tilt angle of 28.5degrees of the three alkyl chains from the surface normal was fabricated and characterized.

Study of molecular orientation in Langmuir-Blodgett films by FTIR

The structure information of orientation and packing of molecular chains can be obtained from infrared transmission and reflection-absorbance (RA) spectra. In the present paper, on the basis of Umemura et al., their FORTRAN program of minicomputer was developed and can be run on 486 personal computer. By comparison of infrared transmission and RA intensities, surface enhancement factors and molecular orientation angle were calculated using the above program, and the influence of complex refractive index, angle of incidence, and thickness of LB film were discussed. These results are consistent with that of Umemura et al.

Plasma modification of aromatic polyamide reverse osmosis composite membrane surface

The surface of aromatic polyamide reverse osmosis composite membrane was modified by oxygen and argon plasma. The water permeability of oxygen-plasma-modified membrane increases, and the chlorine resistance of argon-plasma-modified membrane increases. The spectra of the attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy and the contact angle of the water were analyzed to explain the improvement of the two performances of the composite membrane. The carboxyl groups were introduced when modified by oxygen plasma, and cross-linking occurred when modified by argon plasma. (C) 1997 John Wiley & Sons, Inc.

EPITAXIAL CRYSTALLIZATION OF HIGH-DENSITY POLYETHYLENE ON POLYPROPYLENE IN SOLUTION-CAST FILMS

Epitaxial crystallization of high-density polyethylene (HDPE) on isotactic polypropylene (iPP) in solution-cast films has been investigated by electron microscopy. The specimen-tilt technique of electron microscopy has been used to study the structural relationship between HDPE and iPP crystals. HDPE exhibits different crystalline morphologies in the two basic types of iPP spherulite textures, cross-hatched and lathlike regions. In the former, the crystallographic c axis of HDPE lamellae is in the film plane, while in the latter, the c axis of HDPE crystallites is at an angle of about 50-degrees with the normal of the film. In both structural regions of iPP, however, the contact planes of epitaxial growth are (0 1 0) for iPP and (1 0 0) for HDPE.

The aesthetics of he eyes and mouth position in a three-point face schema

Oculographical research of people watching a human face indicates than beholder's eyes stop most often and for the longest period of time on the eyes and the mouth of the face looked at and that they move among these three points most frequently. The position of the eyes and mouth in relation to one another can be described with a single number being a measure of an angle with the vertex in the middle of the mouth and with arms crossing the centers of the eye pupils. The angles were measured from photographs of people from all over the world, as well as of residents of Lublin. Subsequently, the subjects from Lublin were asked to make face schemas by positioning the eyes and the mouth in the way they considered most attractive. The eye-mouth-eye angle of these schemas was measured. Additionally, measurements of the same angle were taken from the faces depicted in icons. The schemas of the most attractive - according to the subjects - faces were characterized by angles approximating the mean angle from the photographs, and significantly greater than the mean angle from the icons.

Electrochemical and FTIR characterization of the self-assembled monolayer of 2-mercaptobenzimidazole on Au(1 1 1)

The behaviour of a self-assembled monolayer of 2-mercaptobenzimidazole (MBI) at the Au(111) electrode has been examined using cyclic voltammetry and in situ FTIR spectroscopy. The charge associated with the reductive desorption is pH independent while the oxidative partial redeposition charge increases when the pH is lowered. This is due to differences between the nature and the solubility of the MBI desorption product. In alkaline and neutral media MBI desorbs as the thiolate. In contrast, in acidic solutions the thiol is the desorbed product. Subtractively normalized interfacial reflection Fourier transform absorption spectroscopy (SNIFTIRS) has been applied to investigate the MBI monolayer in contact with aqueous solutions of different pH. The SNIFTIRS data are in agreement with the electrochemical results. Moreover, quantitative analysis of the IR data provided evidence that adsorbed MBI molecules assume a tilted orientation with an angle of 60±5° between the C2 axis of the molecule and the direction normal to the gold surface. © 2003 Elsevier B.V. All rights reserved.

Investigation and Development of a Fully 3D Tilt Capable Hybrid SPECT - CT System for Dedicated Breast Imaging

X-ray mammography has been the gold standard for breast imaging for decades, despite the significant limitations posed by the two dimensional (2D) image acquisitions. Difficulty in diagnosing lesions close to the chest wall and axilla, high amount of structural overlap and patient discomfort due to compression are only some of these limitations. To overcome these drawbacks, three dimensional (3D) breast imaging modalities have been developed including dual modality single photon emission computed tomography (SPECT) and computed tomography (CT) systems. This thesis focuses on the development and integration of the next generation of such a device for dedicated breast imaging. The goals of this dissertation work are to: [1] understand and characterize any effects of fully 3-D trajectories on reconstructed image scatter correction, absorbed dose and Hounsifeld Unit accuracy, and [2] design, develop and implement the fully flexible, third generation hybrid SPECT-CT system capable of traversing complex 3D orbits about a pendant breast volume, without interference from the other. Such a system would overcome artifacts resulting from incompletely sampled divergent cone beam imaging schemes and allow imaging closer to the chest wall, which other systems currently under research and development elsewhere cannot achieve.

The dependence of x-ray scatter radiation on object shape, size, material composition and the CT acquisition trajectory, was investigated with a well-established beam stop array (BSA) scatter correction method. While the 2D scatter to primary ratio (SPR) was the main metric used to characterize total system scatter, a new metric called ‘normalized scatter contribution’ was developed to compare the results of scatter correction on 3D reconstructed volumes. Scatter estimation studies were undertaken with a sinusoidal saddle (±15° polar tilt) orbit and a traditional circular (AZOR) orbit. Clinical studies to acquire data for scatter correction were used to evaluate the 2D SPR on a small set of patients scanned with the AZOR orbit. Clinical SPR results showed clear dependence of scatter on breast composition and glandular tissue distribution, otherwise consistent with the overall phantom-based size and density measurements. Additionally, SPR dependence was also observed on the acquisition trajectory where 2D scatter increased with an increase in the polar tilt angle of the system.

The dose delivered by any imaging system is of primary importance from the patient’s point of view, and therefore trajectory related differences in the dose distribution in a target volume were evaluated. Monte Carlo simulations as well as physical measurements using radiochromic film were undertaken using saddle and AZOR orbits. Results illustrated that both orbits deliver comparable dose to the target volume, and only slightly differ in distribution within the volume. Simulations and measurements showed similar results, and all measured dose values were within the standard screening mammography-specific, 6 mGy dose limit, which is used as a benchmark for dose comparisons.

Hounsfield Units (HU) are used clinically in differentiating tissue types in a reconstructed CT image, and therefore the HU accuracy of a system is very important, especially when using non-traditional trajectories. Uniform phantoms filled with various uniform density fluids were used to investigate differences in HU accuracy between saddle and AZOR orbits. Results illustrate the considerably better performance of the saddle orbit, especially close to the chest and nipple region of what would clinically be a pedant breast volume. The AZOR orbit causes shading artifacts near the nipple, due to insufficient sampling, rendering a major portion of the scanned phantom unusable, whereas the saddle orbit performs exceptionally well and provides a tighter distribution of HU values in reconstructed volumes.

Finally, the third generation, fully-suspended SPECT-CT system was designed in and developed in our lab. A novel mechanical method using a linear motor was developed for tilting the CT system. A new x-ray source and a custom made 40 x 30 cm2 detector were integrated on to this system. The SPECT system was nested, in the center of the gantry, orthogonal to the CT source-detector pair. The SPECT system tilts on a goniometer, and the newly developed CT tilting mechanism allows ±15° maximum polar tilting of the CT system. The entire gantry is mounted on a rotation stage, allowing complex arbitrary trajectories for each system, without interference from the other, while having a common field of view. This hybrid system shows potential to be used clinically as a diagnostic tool for dedicated breast imaging.

Computational model for prediction of particle degradation during dilute phase pneumatic conveying: the use of a laboratory scale degradation tester for the determination of degradation propensity

The overall objective of this work is to develop a computational model of particle degradation during dilute-phasepneumatic conveying. A key feature of such a model is the prediction of particle breakage due to particle–wall collisions in pipeline bends. This paper presents a method for calculating particle impact degradation propensity under a range of particle velocities and particle sizes. It is based on interpolation on impact data obtained in a new laboratory-scale degradation tester. The method is tested and validated against experimental results for degradation at 90± impact angle of a full-size distribution sample of granulated sugar. In a subsequent work, the calculation of degradation propensity is coupled with a ow model of the solids and gas phases in the pipeline.

Analysis and modeling of heaping behavior of granular mixtures within a computational mechanics framework

This paper presents a continuum model of the flow of granular material during filling of a silo, using a viscoplastic constitutive relation based on the Drucker-Prager plasticity yield function. The performed simulations demonstrate the ability of the model to realistically represent complex features of granular flows during filling processes, such as heap formation and non-zero inclination angle of the bulk material-air interface. In addition, micro-mechanical parametrizations which account for particle size segregation are incorporated into the model. It is found that numerical predictions of segregation phenomena during filling of a binary granular mixture agree well with experimental results. Further numerical tests indicate the capability of the model to cope successfully with complex operations involving granular mixtures.

Airborne transport of Saharan dust to the Mediterranean and to the Atlantic

The Sahara desert is a significant source of particulate pollution not only to the Mediterranean region, but also to the Atlantic and beyond. In this paper, PM 10 exceedences recorded in the UK and the island of Crete are studied and their source investigated, using Lagrangian Particle Dispersion (LPD) methods. Forward and inverse simulations identify Saharan dust storms as the primary source of these episodes. The methodology used allows comparison between this primary source and other possible candidates, for example large forest fires or volcanic eruptions. Two LPD models are used in the simulations, namely the open source code FLEXPART and the proprietary code HYSPLIT. Driven by the same meteorological fields (the ECMWF MARS archive and the PSU/NCAR Mesoscale model, known as MM5) the codes produce similar, but not identical predictions. This inter-model comparison enables a critical assessment of the physical modelling assumptions employed in each code, plus the influence of boundary conditions and solution grid density. The outputs, in the form of particle concentrations evolving in time, are compared against satellite images and receptor data from multiple ground-based sites. Quantitative comparisons are good, especially in predicting the time of arrival of the dust plume in a particular location.

A computational study of segregation in granular material during heaping

A continuum model of the flow of granular material during silo filling using a viscoplastic constitutive relation is presented in this paper. The constitutive model is based on the Drucker-Prager plasticity yield function. The simulation results give a realistic representation of complex features of granular flows during filling processes, such as heap formation and non-zero inclination angle of the material-air interface. The model is also coupled within the same framework with novel micro-mechanical parametrisations and the process of segregation during filling of granular mixtures can also be modelled.

Modelling of dosator operation for improved manufacturing performance

Purpose: To develop an improved mathematical model for the prediction of dose accuracy of Dosators - based upon the geometry of the machine in conjunction with measured flow properties of the powder. Methods: A mathematical model has been created, based on a analytical method of differential slices - incorporating measured flow properties. The key flow properties of interest in this investigation were: flow function, effective angle of wall friction, wall adhesion, bulk density, stress ratio K and permeability. To simulate the real process and (very importantly) validate the model, a Dosator test-rig has been used to measure the forces acting on the Dosator during the filling stage, the force required to eject the dose and the dose weight. Results: Preliminary results were obtained from the Dosator test-rig. Figure 1 [Omitted] shows the dose weight for different depths to the bottom of the powder bed at the end of the stroke and different levels of pre-compaction of the powder bed. A strong influence over dose weight arising from the proximity between the Dosator and the bottom of the powder bed at the end of the stroke and the conditions of the powder bed has been established. Conclusions: The model will provide a useful tool to predict dosing accuracy and, thus, optimise the future design of Dosator based equipment technology – based on measured bulk properties of the powder to be handled. Another important factor (with a significant influence) on Dosator processes, is the condition of the powder bed and the clearance between the Dosator and the bottom of the powder bed.