Changes In Surface Configuration Research Articles

Apophis 2029: Decadal Opportunity for the Science of Planetary Defense

Many advancements in planetary science are achieved by seizing upon the opportunity created by rare natural events (e.g. comet Shoemaker-Levy 9 Jupiter impact; 1994) and by planned physical interactions (e.g. Deep Impact into comet Tempel 1; 2005). A forthcoming opportunity to seize upon a natural physical “experiment” occurs on April 13, 2029 with the unprecedentedly close Earth encounter by the large 340m asteroid (99942) Apophis. On that date, nature is performing the “experiment” of subjecting the physical body of Apophis to Earth’s tidal torques as it approaches to within 31,000 km of Earth’s surface, a distance that is closer than orbiting geosynchronous satellites. A potentially hazardous asteroid (PHA) as large as Apophis encountering Earth this closely (within 0.1 lunar distances) is, on average, a once-per-thousand year event. (In context, Apophis is 7 times larger and 350 times more massive than the Tunguska 1908 impactor; 5000 times more massive than Chelyabinsk 2013.) Because of this event’s incredible rarity, knowledge gained through measurements and outcomes of the Apophis 2029 “natural experiment” are clearly a decadal, if not millennial, opportunity for planetary science. Most specifically, this knowledge opportunity is for the science supporting planetary defense. Further, on April 13, 2029 all of Earth will be watching: Apophis will be visible to the naked eye speeding across the evening sky for an estimated 2 billion people spanning western Europe and northern Africa. In this White Paper we outline our current best understanding, and uncertainties, for scientific advances in the physical study of potentially hazardous asteroids that may be achievable by measuring physical changes of Apophis’ spin, surface structure, and/or shape configuration in response to Earth’s tidal torques. If tidal torques themselves, or surface configuration changes induce any measurable seismic vibration signal inside Apophis, a new field of asteroid seismology has the potential to be born. Over six decades of planetary science, seismology has been achieved beyond Earth for only two planetary worlds: Moon and Mars. With this White Paper, we take no position on how to implement specific investigations capable of achieving the science advances offered by the Apophis 2029 opportunity. Instead we advocate that competitive selection of investigations, be they theoretical or observational (ground-based, space-based, or in situ), be executed under the direction of NASA’s Planetary Defense Coordination Office, with a projected and perhaps necessarily augmented budget capable of supporting them. International collaboration is strongly encouraged. Thus, summarizing in four specific points, we urge the framers of the Decadal Survey to: • Recognize the decadal, if not millennial, opportunity for the science of planetary defense presented by the Apophis 2029 once-per-thousand-year “natural experiment.” • Prioritize as a top-level planetary defense science goal modeling and measuring the physical outcome on Apophis exerted by Earth’s tidal torques so as to achieve the greatest possible new insights into the physical nature, including the internal structure, of PHAs. • Recognize that time is of the essence for defining and implementing investigations of physical effects on Apophis, particularly if in situ measurements are to be considered. An Apophis 2029 Science Definition Team may be prescribed. • Recognize that the achievable knowledge of PHAs presented by the Apophis 2029 opportunity could have immeasurable benefits to the future of humanity, in the highly unlikely, but not impossible necessity to mitigate a future impact threat

Hydraulic Performance of Concrete Block Pavement under High Rainfall Intensities

High rainfall intensity will generate different response on the concrete block pavement (CBP) performance. A study found that larger openings of CBP did not lead more water penetrated. In other study, larger openings can lead greater decrease in runoff velocity. The correlation between the openings, water penetration and runoff velocity has remained unclear. In this study, we investigated hydraulic performance of CBP as an impact of surface roughness condition, under high rainfall intensities, saturated sub-base layer, and various slope surfaces. We conducted experiment using a 2 m by 6 m of rectangular CBP layer with herringbone 90 and basket-weave pattern. We used a modified dye tracing method in view to monitor the surface flow velocity under various high rainfall intensities. The results showed that hydraulic performance of surface runoff in the CBP layer was more influenced by the surface roughness condition. The roughness condition was very sensitive to the change in surface configuration of the CBP. The relationship between rainfall intensity, surface slope and roughness number followed polynomial functions. A further study is required to investigate the appropriate quality of CBPs, which have high durability applied over a steep slope surface and under high rainfall intensities.

Multiple adsorption of tributyl phosphate molecule at the dyed-TiO2/electrolyte interface to suppress the charge recombination in dye-sensitized solar cell

Electron recombination and dye aggregation at the dyed-TiO2/electrolyte interface are still problems in dye-sensitized solar cell (DSC) research. In this paper, tributyl phosphate (TBpp) as a special additive to modify the dyed-TiO2/electrolyte interface was introduced to enhance the photovoltaic performance. The adsorption mode of TBpp and the interaction between cis-dithiocyanate-N,N′-bis-(4-carboxylate-4-tetrabutylammonium carboxylate-2,2′-bi-pyridine) ruthenium(II) (N719) and TBpp were investigated. It was found that one TBpp parent molecule split into several smaller fragments and formed four anchoring modes on the TiO2 surface. It was very interesting that the molecular cleavage of TBpp and adsorption of N719 assisted each other on the sensitized TiO2 surface. The fragments distributed around N719 result in steric hindrance, consequently hydrogen-bonding among N719 molecules was decreased. The unstable type N719 transformed into stable type N719 accompanied by molecular cleavage of TBpp and the N719 aggregation was reduced. Furthermore, these new fragments were multiply adsorbed on the non-sensitized TiO2 surface to form an insulating barrier layer. Therefore, the electron recombination at the dyed-TiO2/electrolyte interface was restrained. Besides the change of surface configuration, the TiO2 band edge negatively shifted and the rate of electron transport in the TiO2 films decreased with the addition of TBpp. As a result, an increase in the photoelectric conversion efficiency (η) was obtained of almost 40%.

Adsorption of Salivary Proteins on Titanium Implants

A major factor that contributes to the failure of a dental implant is peri-implantitis, which develops as a result of bacterial colonization onto the implant surface. Bacterial plaque formation to the intra-oral hard surface is dependent on surface roughness or pellicle adsorption. Early events in pellicle formation may affect plaque composition and pathogenesis. Recent studies showed that bacterial adherence to salivary coated biomaterials had unique characteristics mainly due to the different pellicle adsorption pattern onto diverse substratum. Titanium(Ti) implants present a different surface configuration from enamel and thus may alter plaque composition. Moreover, a surface modified Ti implant has variable surface characteristics according to the modification methods. The present study was designed to qualitatively characterize the pellicle adsorption pattern of the plasma sprayed Ti implant compared to enamel surface in vivo. Enamel slabs and plasma sprayed Ti implants were attached to the buccal surface of a vacuum-formed splint using dental floss silk. The splint was held in the volunteer’s mouth for 2 hours. The adsorbed pellicles were extracted from the substrates and lyophilized. Human whole saliva(HWS), human parotid saliva(HPS) and human submandibular-sublingual saliva(HSMSL) were also collected from the same subject. Salivary proteins components were analyzed by SDS-PAGE gel electrophoresis and Western blot analyses. SEM assessment was also conducted to identify the surface configuration changes. Results showed that the plasma sprayed Ti implant pellicle contains different salivary protein component from enamel surface and the protein component came primarily from HSMSL saliva, while amylase, sIgA and lactoferrin existed both in TiP and EP, the blotting intensity was different. A two hour adsorbed pellicle laid

Fluid-Holding Time Parameter and Fluid Holding Capability of Polymeric Materials

The fluid holding capability of polymeric materials was semiquantitatively characterized with a new parameter called the fluid holding time (FHT). FHT measures the time it takes a continuous film to recede down the side of a Wilhelmy plate, which varies on different surfaces with the same degree of wettability. Both pure water and an artificial tear fluid (i.e., protein/salt solution) were used to systematically wet uncoated and plasma polymer coated polymeric plates. The FHT was calculated from Wilhelmy force loop plots in the event that a continuous water or aqueous film adhered to a polymeric surface. Such events are easily verified by consecutive wetting. Dynamic Wilhelmy force measurement is probably the most sensitive technique for monitoring wettability and surface configuration change, two important phenomenological factors that affect the FHT. The FHT measured by the Wilhelmy balance method can be effectively used to compare the liquid holding capabilities of different surfaces. The value of the ...

The investigation of polymer surface dynamics modified by plasma using dynamic contact angle method

According to the changes of surface dynamic decay rate constant and dynamic contact angle hysteresis in the entire range of CF 4(%) in CF 4/CH 4 plasma feed gas, the whole range can be divided into three regions, which are distinguished by their different plasma reaction mechanistic and properties of the polymerized films. The rate constant of first water immersion stage for polymer films pretreated by CH 4 plasma, and then treated by CF 4/CH 4 plasma is smaller than that of unpretreated films. This demonstrated that an ultrathin layer of plasma polymer of methane as a barrier layer, placed prior to CF 4/CH 4 plasma treatment, can significantly reduced the decay. Arrhenius plots of the decay rate constants on the water immersion temperature showed conspicuous breaks at characteristic surface transition temperature T s, which represents the change of driving force due to the change in basic properties of water in contact with a surface at the Drost-Hansen temperature of 15°C. The activation energy for the surface configuration change at above and below T s is relatively small. The basic nature of the surface configuration change is relatively simple rotational motion without involving large segments or migration of whole macromolecules.

Modification, degradation, and stability of polymeric surfaces treated with reactive plasmas

The degradation, modification, and stability of polymeric surfaces exposed to chemically reactive O2 and H2O-vapor plasmas were investigated. Specifically, the effects of these plasmas on etching rate, surface morphology, wetting instability, and fluid-holding capability were studied. Wetting instability is reflected by hydrophobic recovery and can be examined by the Wilhelmy balance method. Although hydrophobic recovery is usually attributed to surface configuration change, there are actually two types: reversible and permanent. Reversible hydrophobic recovery is caused by surface configuration change, whereas permanent hydrophobic recovery is caused by the creation of oxidized surface oligomers. This study distinguishes the two by identifying differences in the shapes of the corresponding Wilhelmy force loops and in the fluid-holding parameter. The presence of surface oligomers was most detrimental to wetting stability and fluid-holding capability but could be controlled via the type of reactive gas, the discharge conditions, and the polymer substrate. In general, polymers most susceptible to O2-plasma etching had the least surface oligomers and vice versa, whereas H2O-vapor plasma suppressed surface oligomers on polymers less susceptible to etching. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3028–3042, 2000

Surface Modification of Conventional Polymers by Depositing Plasma Polymers of Trimethylsilane and of Trimethylsilane + O2: II. Dynamic Wetting Properties

The dynamic wetting properties of TMS (trimethylsilane) and TMS + O2plasma-deposited films on ten low energy conventional polymers were investigated using the Wilhelmy balance method. Plasma deposition resulted in wetting properties that were independent of the underlying polymer substrate for the majority of polymers studied. TMS plasma modification resulted in virtually the same degree of hydrophobicity with an average cosine of the dynamic advancing contact angle from the first immersion, cos θD,a,1= −0.381 (θD,a,1= 112 ± 3.6), for eight of the ten polymers. PTFE and UHMWPE were slightly more hydrophobic after TMS plasma treatment with an average cos θD,a,1= −0.785 (θD,a,1= 141 ± 4.2). TMS + O2plasma modification resulted in high wettability of all polymers with an average cos θD,a,1= 0.654 (θD,a,1= 49.2 ± 11.7). Dynamic hysteresis, mainly a result of the change in meniscus shape during immersion and emersion, and intrinsic hysteresis, due to the extent of surface configuration change, were both found to vary according to the size of the polymer plate. In general, dynamic hysteresis can be quite large for more hydrophobic TMS treated polymers and considerably smaller for highly hydrophilic TMS + O2treated polymers. The extent of intrinsic hysteresis of only TMS treated polymers was found to be independent of the underlying polymers within the time-scale of wetting. TMS + O2plasma treatment resulted in wide variations in intrinsic hysteresis probably due to substrate specific etching of oxygen plasma species. The wettability of the untreated and TMS and TMS + O2treated polymers, indicated by the static “advancing” contact angles from the sessile droplet method and dynamic “advancing” and “receding” contact angles from the Wilhelmy balance method, were found to conform well to the correlation, cos θS= (cos θD,a,1+ cos θD,r,1)/2.

Surface Dynamics of Plasma Polymers Studied by the Wilhelmy Force Measurement

Surface dynamic change during the Wilhelmy force measurement was investigated for microscope cover glasses coated by trimethylsilane (TMS) and TMS + oxygen plasma polymers. The intrinsic hysteresis which is caused by the surface configuration change on water immersion can be detected by the deviation of shape of the force loop. The deviation of the second immersion line from the first immersion line and also of the initial slope of the second immersion (in the transient stage where the change of meniscus takes place) can be taken as a measure of the existence and the extent of the surface dynamic changes due to water immersion. These parameters are dependent on the speed of immersion or emersion employed in the force measurement and can be enhanced by halting the motion at the end of immersion or emersion.

FEMORAL COMPONENT WEAR IN RETRIEVED HIP PROSTHESES

We retrieved 159 femoral heads at revision surgery to determine changes in surface configuration. Macroscopic wear of the head was observed in three bipolar hip prostheses as a result of three-body wear. There was a considerable change in surface roughness in the internal articulation of bipolar hip prostheses. Roughness in alumina heads was almost the same as that in new cobalt-chromium heads. The annual linear wear rate of polyethylene cups with alumina heads was less than that of cups with cobalt-chromium alloy heads. Polyethylene wear was increased in the prostheses which had increased roughness of the head.

Surface Configuration Change Observed for Teflon-PFA on Immersion in Water

The oxygen atoms in a dry film of a copolymer of tetrafluoroethylene (97 mol %) and perfluoropropyl vinyl ether (3 mol %) are hardly detecta.ble by ESCA because the atomic percent of oxygen in the copolymer is small and oxygen atoms are not likely to be found in the outer region of a dry surface. When the film is immersed in liquid water, however, a conspicuous O 1s peak appears on the ESCA spectrum, and its intensity increases with the immersion time. The advancing and receding contact angles measured by the sessile droplet method deviate from those for a dry film progressively with water immersion time. When the surface tension of water is lowered by adding a small amount (0.01%) of a surfactant (Scourol 400) or ethanol (50 vol %), the surface configuration change decreases according to the decrease in the surface tension of the liquid. The maximum extent of the surface configuration change is correlated to the differential surface tension (the difference between the solid surface tension and the liquid surface tension). The greater the differential surface tension, the larger the extent of surface configuration change that occurs to minimize the interfacial tension.

The Driving Force and the Process of Mass Transport in the Solid State Sintering

The problems of the Thomson-Freundlich equation in the solid state sintering are pointed out, which has been used as the relationship concerned with the chemical potential difference, surface curvature and vacancy concentration gradient. Based on the view point of the variation in total system energy as the driving force of the solid state sintering, the new concept of the reduction in local surface energy is introduced, and with the new introduced concept of the reduction in local surface energy, the change of surface configuration by surface diffusion is two dimensionally discussed.

Dynamics of the surface configuration change of polymers in response to changes in environmental conditions. 2. Comparison of changes in air and in liquid water

Dynamics of the surface configuration change of polymers in response to changes in environmental conditions. 2. Comparison of changes in air and in liquid water

Changes in surface configuration of the skin caused by ageing and application of cosmetics: three‐dimensional analysis according to a new system based on image analysis and Fourier transformation

Synopsis The surface configuration of the skin, as characterized by surface furrows and plateaux, is known to change with ageing and skin condition. There have been many attempts to analyse the surface configuration in order to evaluate the effect of skin care products. However, the systems proposed up to now are insufficient to obtain three-dimensional data. A system based on image analysis and Fourier transformation has been developed. By using this system, we can make a quick and quantitative analysis of the three-dimensional surface configuration of the skin. This system was applied to measure changes in the surface configuration with ageing, and to clarify the effects of cosmetic cream. As a result, it was found that the furrows become less clear, become parallel in one direction and the texture becomes coarse and irregular, as ageing continues. These changes are believed to correspond to deterioration of the metabolic and moisturizing functions of the skin. It was also found that the furrows become clear and the texture becomes finer after the application of cream than before. This is believed to be the result of the improvement of the skin condition due to the moisturizing effect of the cream.

Low temperature and conventional scanning electron microscopy of human urothelium.

The appearance of fixed dehydrated non-neoplastic human urothelium viewed by conventional scanning electron microscopy (CSEM) is different from that of frozen hydrated human urothelium viewed by low temperature scanning electron microscopy (LTSEM). In the fixed dehydrated material the surface is formed by well defined, polygonal, domed superficial urothelial cells which have prominent surface microridges. In places intermediate urothelial cells are visible and they have surface microvilli. In the frozen hydrated material viewed by LTSEM most of the surface is smooth. This is formed in part by a glutaraldehyde soluble extracellular secretion which may be a mucin barrier to bacteria. We believe that the rest of the smooth surface is formed by superficial urothelial cells which are not well defined and which lack microridges. There are islands of rounded cells lacking microvilli which are probably intermediate urothelial cells as they correspond in appearance with the intermediate urothelial cells seen in freeze fractured material. It seems likely that fixation and dehydration will cause some change in surface configuration and in theory the frozen hydrated material should more closely resemble the natural state. We believe that LTSEM will be of value in investigating normal and diseased urothelium.

Numerical solution of subsonic compressible flow at two-dimensional inlets.

K of the subsonic flowfield in the vicinity of air inlets or wedges is a necessity for engineering design and analysis. This Note presents the results of numerical solutions for two-dimensional subsonic compressible flows. In order to obtain a solution it is necessary to introduce several severe restraints such as field representation, field boundaries, and body surface configuration changes. The effects of these restraints have been investigated and the optimum methods are presented. Emmons, Amick, and other investigators' have treated the various methods of solution of the simultaneous difference equations that represent the continuous flowfield in terms of a discretized flowfield. Fox has presented some methods for representing the discontinuous finite slope changes of bound-