Low Take-off Angles Research Articles

Clustering technical approaches of elite and world-class pole vaulters based on 10 years of measurement during competitions

ABSTRACT Recently, a variety of technical approaches in world-class pole-vaulters’ behaviour have been observed. The aim of this study was to investigate the presence of subgroups using different technical approaches and to compare biomechanical performance differences. Biomechanical analysis of performances over 5.00 metres from 99 athletes were clustered with K-means methodology based on the relative position of the top hand at take-off and the direction of the top of the pole from take-off to the maximal pole bending. Analysis revealed four subgroups that were distinguished by higher and lower direction angle and relative position values. Despite differences in technique, the analysis did not reveal significant differences between these four groups in performance, take-off speed, or athlete anthropometrics. Nevertheless, these clusters showcased variations in pole–athlete interactions and pole bending, suggesting different strategies and physical requirements associated with each approach. Cluster 2 characterised the classical technique with a high direction angle and a take-off position close to the vertical plane. Cluster 4 displayed a technique with a low take-off angle, suggesting the influence of athletes like Lavillenie, in deviating from the conventional model. Understanding and categorising athletes based on their preferred technique can aid coaches in providing tailored instructions, leading to performance improvements.

X-ray excited Auger Cu L3L4,5M4,5 spectra measured at low take-off angles as a fingerprint for a Cu‐organics connection

In this work, surface analysis by measuring high-resolution Auger Cu L3L4,5M4,5 spectra was performed at very low take-off angles using X-ray photoelectron spectroscopy. The focus of this research was on determining if a fingerprint feature exists for a specific connection between Cu(I) (and/or Cu(II)) and different organic molecules. These organic molecules were adsorbed on Cu surface from 3wt.% NaCl solution containing a 1mM concentration of organic compound, i.e. 4‐methyl‐2-phenylimidazole, benzotriazole, 3‐amino-1,2,4-trazole, 1,2,4‐triazole, 2‐mercaptobenzimidazole, 2‐mercaptobenzoxazole, 2‐mercaptobenzothiazole, 1‐hydroxybenzotriazole, and 2-mercapto-1-methylimidazole. This feature was shown to be connected to Cu(I)- and/or Cu(II)-complex formation.

Jumping without slipping: leafhoppers (Hemiptera: Cicadellidae) possess special tarsal structures for jumping from smooth surfaces

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers (Philaenus spumarius, Aphrophoridae) and leafhoppers (Aphrodes bicinctus/makarovi, Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs of Philaenus froghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces. By contrast, Aphrodes leafhoppers took off without their propulsive hind legs slipping, and reached low take-off angles and high velocities on both substrates. This difference in jumping ability from smooth surfaces can be explained not only by the lower acceleration of the long-legged leafhoppers, but also by the presence of 2–9 soft pad-like structures (platellae) on their hind tarsi, which are absent in froghoppers. High-speed videos of jumping showed that platellae contact the surface briefly (approx. 3 ms) during the acceleration phase. Friction force measurements on individual hind tarsi on glass revealed that at low sliding speeds, both pushing and pulling forces were small, and insufficient to explain the recorded jumps. Only when the tarsi were pushed with higher velocities did the contact area of the platellae increase markedly, and high friction forces were produced, consistent with the observed jumps. Our findings show that leafhoppers have special adhesive footpads for jumping from smooth surfaces, which achieve firm grip and rapid control of attachment/detachment by combining anisotropic friction with velocity dependence.

XPS depth profiling of derivatized amine and anhydride plasma polymers: Evidence of limitations of the derivatization approach

The quantitative analysis of the chemistry at the surface of functional plasma polymers is highly important for the optimization of their deposition conditions and, therefore, for their subsequent applications. The chemical derivatization of amine and carboxyl-anhydride layers is a well-known technique already applied by many researchers, notwithstanding the known drawback of the derivatization procedures like side or uncomplete reactions that could lead to “unreliable” results. In this work, X-ray photoelectron spectroscopy (XPS) combined with depth profiling with argon clusters is applied for the first time to study derivatized amine and carboxyl-anhydride plasma polymer layers. It revealed an additional important parameter affecting the derivatization reliability, namely the permeation of the derivatizing molecule through the target analysed layer, i.e. the composite effect of the probe molecule size and the layer porosity. Amine-rich films prepared by RF low pressure plasma polymerization of cyclopropylamine were derivatized with trifluoromethyl benzaldehide (TFBA) and it was observed by that the XPS-determined NH2 concentration depth profile is rapidly decreasing over top ten nanometers of the layer. The anhydride-rich films prepared by atmospheric plasma co-polymerization of maleic anhydride and C2H2 have been reacted with, parafluoroaniline and trifluoroethyl amine. The decrease of the F signal in top surface layer of the anhydride films derivatized by the “large” parafluoroaniline was observed similarly as for the amine films but the derivatization with the smaller trifluoroethylamine (TFEA) led to a more homogenous depth profile. The data analysis suggests that the size of the derivatizing molecule is the main factor, showing that the very limited permeation of the TFBA molecule can lead to underestimated densities of primary amines if the XPS analysis is solely carried out at a low take-off angle. In contrast, TFEA is found to be an efficient derivatization agent of anhydride groups with high permeability through the carboxyl-anhydride layer.

Water-induced surface structure of poly(dimethylsiloxane)-containing block copolymers

Two triblock copolymers, polyester-b-poly(dimethylsiloxane) (PDMS)-b-polyester, were synthesized by the ring-opening polymerization with both hydrophobic and water-repellent hydroxyl-terminated PDMS and hydrolytically degradable ester monomers. The Tgs of the polyester blocks were controlled by ɛ-caprolactone/lactide mixture or lactide only. The surface composition of the triblock copolymers was measured by angle-dependent electron: X-ray photoelectron spectroscopy. The results showed that the PDMS block with a low surface energy in the copolymers was quite segregated in the surface region; the copolymer films showed significantly higher mole fractions of PDMS (0.78–0.86) at a low takeoff angle compared with their bulk mole fractions (0.015–0.02). When the films were exposed to water at 20 °C for 70 min, the mole fractions of surface PDMS were decreased to 0.3–0.5 because of the water-repellent hydrophobicity and the chain mobility of both blocks. Open image in new window

Enhancing the hole injection ability of indium tin oxide viaammonium salts in polymer light-emitting diodes

The enhancement of the hole injection ability of indium tin oxide (ITO) by spin-coating ammonium salts onto it is investigated. The work function of the ITO is increased via spin-coating an NH4Br aqueous solution onto it, which is observed using ultra-violet photoelectron spectroscopy. The formation of H-bonds at the interface between the ITO and the NH4Br is corroborated by utilising the surface sensitivity of synchrotron X-ray photoelectron spectroscopy at low photoelectron take-off angles. We illustrate the increase in the work function of the ITO with a possible scheme involving H-bonding between NH4+ and the ITO. Polymer light-emitting diodes (PLEDs) with ITO/NH4Br showed significantly enhanced performances compared to those with ITO only, with higher current density (924 mA cm−2vs. 903 mA cm−2) and brightness (44 224 cd m−2vs. 1987 cd m−2) at a bias voltage of 7.0 V. To confirm the advantages of general ammonium salts for enhancing device performance, PLEDs with ITO coated by NH4Cl, NH4H2PO4, and (NH4)2SO4 were fabricated and their performances were verified.

Weight Loading and Reproductive Status Affect the Flight Performance of Pieris napi Butterflies

Weight-induced mobility reductions can have dramatic fitness consequences and winged animals are especially sensitive to the trade-off between mass and locomotion. Data on how natural weight fluctuations influence a flying insect’s ability to take off are scarce. We therefore quantified take-off flight ability in Pieris napi butterflies in relation to reproductive status. Take-off flight ability (velocity and take-off angle) under suboptimal temperature conditions was recorded with a 3D-tracking camera system and was predicted to decrease with relatively larger weight loads. Our results show that relatively larger weight loads generally reduce flight speed in male butterflies and lower take-off angles in females. However, despite having a lower wing loading, mated male butterflies flew slower than unmated males. Our study suggests that retention of weight loads associated with reproduction impairs insect flight performance.

Selective Backscattered Electron Imaging of Material and Channeling Contrast in Microstructures of Scale on Low Carbon Steel Controlled by Accelerating Voltage and Take-off Angle

We studied the behaviors of contrast in backscattered electron (BSE) images of cross-sectional heat-treated steel under various accelerating voltages and take-off angles. Changes in these conditions resulted in dramatic changes in contrast. Low accelerating voltage and low take-off angle improved the surface information and channeling contrast, whereas high accelerating voltage and high take-off angle enhanced the bulk information and reduced channeling contrast, resulting in improved Z contrast. Such behavior can be understood by the ratio of low-loss electrons (LLEs), which are related to channeling contrast, to the inelastic BSE components detected. The distribution of these components varies with the accelerating voltage and take-off angle: the detection ratio of LLE to inelastic BSE increases with decreasing accelerating voltage and take-off angle. The results obtained in this study will be useful for obtaining Z and crystallographic information separately in BSE images for the material of interest.

Selective Backscattered Electron Imaging of Material and Channeling Contrasts in Microstructures of Scale on Low Carbon Steel Controlled by Accelerating Voltage and Take-off Angle

The behaviors of contrasts in backscattered electron (BSE) images of cross-sectional heat-treated steel are studied under various accelerating voltages and take-off angle conditions. Changes in these conditions resulted in dramatic changes in contrasts. Low accelerating voltages and low take-off angles improve surface information and channeling contrasts, whereas high accelerating voltages and high take-off angles enhance bulk information and reduce channeling contrasts, resulting in improved Z contrast. These behaviors can be understood by the ratio of LLE (Low-Loss Electron), which are related to channeling contrasts, to the inelastic BSE components detected. The distribution of these components varies depending on the accelerating voltage and take-off angle, in that the detection ratio of LLE to inelastic BSE increases with decreasing accelerating voltages and take-off angles. The results obtained in this study can be used for obtaining Z and crystallographic information separately in BSE images for the material of interest.

Synthesis of polyester/poly(dimethylsiloxane)/polyester triblock copolymers and their rearrangement under water: rearrangement of PDMS-containing copolymers

Triblock copolymers consisting of a poly(dimethylsiloxane) (PDMS, Mn = 1000) middle block coupled to hydrolytically degradable polyester end blocks having different glass transition temperatures (T g) as a newly developed biomaterial were synthesized by ring open polymerization initiated by both alcohol end groups of PDMS. 1H-NMR and X-ray photoelectron spectroscopy (XPS) were used to determine the bulk and surface compositions of the copolymers. Quantitative angle-dependent XPS data from cast thin films of the copolymers showed significantly high mole fractions of PDMS (0.7–0.92) at low takeoff angles as opposed to low mole fractions of PDMS (0.009–0.065) in the bulk. XPS data also showed that exposing the film to water significantly effect the surface composition of which PDMS concentration was decreased. This suggests that the copolymer chains undergo a structure rearrangement at the polymer water interface, depending on both T gs of polyester blocks in the copolymers and immersing time.

Optimum take-off angle in the long jump

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles.

X-ray photoelectron diffraction study of an anatase thin film: TiO 2(001)

An anatase thin film, TiO 2(001), has been grown by metal–organic chemical vapor deposition on a SrTiO 3(001) substrate. The electronic and structural properties of the anatase thin film were investigated by X-ray photoelectron spectroscopy, low energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD). Comparisons of the core-level binding energies for O 1s and Ti 2p 3/2 photoelectrons was made between anatase and rutile, and were found to be identical for both polymorphs. Structurally, the surface gave a (1×1) LEED pattern with a high background, indicating regions of good long-range order. Comparison between experimental XPD data and single-scattering cluster calculations indicate that there is good agreement with an anatase crystal termination, and poor agreement with a rutile crystal termination. Furthermore, good agreement was found at low takeoff angles for experiment and calculations suggesting that the thin film has good short-range order at the surface. This study indicates that anatase is stable and does not undergo a transformation to the rutile polymorph when exposed to atmosphere after film growth or after heating to low temperatures in ultrahigh vacuum.

Mixed self-assembled monolayers of terminally functionalized thiols at gold surfaces characterized by angle resolved X-ray photoelectron spectroscopy (ARXPS) studies

The adsorption of non-reactive alkanethiols and cyano-terminated thiols possessing the same chain length as well as their mixtures were examined on polycrystalline gold surfaces by angle resolved X-ray photoelectron spectroscopy (ARXPS). The adsorption behavior was investigated based on the chemical shift of the S 2p peak components. Besides the expected bound state of the thiols at the surface, non-bound molecules were detected with an increasing intensity at lower take-off angles. The layer composition does not entirely reflect the solution composition and the degree of adsorption is independent of the solution composition. A preferential adsorption of the methyl-terminated alkanethiol at the polycrystalline gold surface was measured.

Ultra thin film sputter depth profiling

As semiconductor device geometry continues to shrink, new ultra thin material systems are developed. One such structure is a thin silicon oxy-nitride (ONO) film used in memory devices. Secondary Ion Mass Spectrometry (SIMS), because of its extreme surface sensitivity (small sampling depth), is routinely used to study thin ONO structures. However, interpretation and quantification of SIMS data is often difficult because of matrix effects that impact the secondary ion yield of different chemical species. With the Quantum 2000 Scanning ESCA MicroprobeTM, it is possible to obtain surface sensitivity equivalent to SIMS, using a low (20°) photoelectron take-off angle. The resulting ESCA data contain quantitative chemical state information that is difficult to obtain by other methods.

The effect of large solid angles of collection on quantitative X-ray microanalysis in the AEM.

Increasing the solid angle of X-ray collection is a major factor in improving the analytical sensitivity of X-ray energy-dispersive spectrometry (XEDS) in the analytical electron microscope (AEM). A new scanning transmission electron microscope, the VG HB 603, is equipped with two XEDS detectors with the largest collection angles (0.30 and 0.17 sr) available in commercial AEMs. However, large collection angles result in a large range of take-off angles, from approximately 4 degrees to 36 degrees, and the low angles can cause strong X-ray absorption. In order to investigate possible detrimental effects of the low (and of the range of) take-off angles on quantitative microanalysis of specimens exhibiting significant absorption, a stoichiometric Ni3Al thin-film, in which the Al Kalpha line is significantly absorbed, was analysed. Furthermore, the effect of different values of the collection angle on X-ray intensities was theoretically evaluated by numerical calculations and spectral simulation. These theoretical approaches permitted correlation of changes in the X-ray take-off angle (and hence X-ray absorption) with changes in the collection angle. It is demonstrated that approximately 0.30 sr detectors, with minimum take-off angles as small as 4 degrees, only result in maximum errors of 4% in the quantification of Al in Ni3Al and, therefore, further increases in collection angle can be pursued while maintaining current levels of accuracy of quantification.

Synthesis of a new photoreactive derivative of dipyridamole and its use in the manufacture of artificial surfaces with low thrombogenicity.

Photoimmobilization of dipyridamole (Persantin) was accomplished through the use of a new synthetic conjugate molecule, 1. Persantin is a powerful inhibitor of platelet activation and aggregation and is widely used as a vasodilator. Conjugate 1 consists of triply protected dipyridamole [three of the four hydroxyl groups carry a tert-butyldimethylsilyl (TBDMS) protective group) and the photoreactive 4-azidobenzoyl group. A short hydrophilic spacer chain, derived from triethylene glycol, separates the protected dipyridamole system and the photoreactive group. Compound 1 was immobilized on polyurethane sheets (Pellethane D-55) through irradiation with ultraviolet (UV) light, and the protective groups were removed afterward. The resulting modified polyurethane surfaces were characterized by different physicochemical techniques: UV extinction, contact angle measurements (captive bubble technique), and X-ray photoelectron spectroscopy (XPS). The UV extinction measurements showed the presence of 13 +/- 1 nmol of immobilized dipyridamole/cm2. The contact angle measurements revealed that the modified surface was markedly more hydrophilic than the control (i.e. unmodified polyurethane). XPS measurements clearly established the presence of immobilized dipyridamole in the outermost layers of the modified surface. This was especially clear from the XPS spectra recorded at a low take-off angle (approximately 6 degrees). Furthermore, the XPS spectra showed that the TBDMS protective groups had been quantitatively removed during the deprotection/washing treatment. The in vitro blood compatibility of the modified surface was studied with the thrombin generation assay as developed in our group, as well as with scanning electron microscopy. The thrombin generation test produced a lag time of 1275 s for the modified surface, as opposed to 569 s for the control. Scanning electron microscopy showed that far fewer platelets adhere to the modified surface (approximately 7 x 10(3)/mm2) as compared to the control (approximately 6 x 10(2)/mm2). Taken together, the experimental data reveal that the modified surface has excellent blood compatibility in vitro. It is discussed that the use of conjugate 1 leads to simultaneous exposure of dipyridamole at the modified surface and to a marked increase of the surface hydrophilicity, which is likely to hamper adsorption of plasma proteins. The combination of these effects is uniquely related to the molecular buildup of 1. Conjugate 1 will be used in future work that is aimed at preparing small-caliber polyurethane vascular grafts with a blood compatible lumenal surface.

ZAF, PAP, Φ(ρz), α-FACTOR..: A Comparison of the Relative Accuracies of The Alphabet Soup of Correction Factors for “Non-Optimized” Samples

The ultimate practical test of the utility of a correction procedure for quantitative x-ray microanalysis is how well the analyses of standards of interest conform to their known compositions. Many papers have been published testing various correction algorithms by processing data from sets of quantitative analyses through the corrections and then comparing the resulting error histograms {e.g., Fig. 1). The best correction procedure is usually considered to be the method that results in error histograms with the minimum mean relative error and the smallest standard deviation for the distribution of relative errors. Such evaluations can be misleading for a number of reasons: (1) the correction procedure may have been “adjusted” by adding empirical factors to produce superior results for a particular type of specimen. If the test data either include these data or include samples of similar composition to those employed for the refinement, the results may appear artificially good and may not work nearly as well for other types of specimens. (2) The analytical data used for testing may itself be flawed, either because the samples were not actually the compositions they were thought to be (or the sample surface analyzed was not the same composition as that published for the bulk material); or because the surface or the sample was contaminated, rough or charging; or because the analytical conditions were not well controlled. (Many of the published k-factors used in evaluating correction procedures [e.g., ref. 1] were obtained in the early days of microbeam analysis, using instruments having poor control over high voltage and beam current stability with low spectrometer take-off angles.) (3) The analytical data may contain specimens analyzed under unusual conditions {e.g,, very high or veiy low accelerating potentials) that may have very large corrections dominating the data set that may never be encountered in normal analysis.

Characterization of PTFE on Silicon Wafer Tribological Transfer Films by XPS, Imaging XPS and AFM

Atomic force microscopy (AFM) shows that PTFE-on-silicon wafer tribological transfer films consist of narrow ribbons of PTFE, <1 μm wide and <10 nm high, aligned with the film draw direction. Within the ribbons the PTFE molecular chains are also aligned with the draw direction. Such materials are of interest as substrates for the epitaxial crystallization of polymers and small molecules. X-ray photoelectron spectroscopy demonstrates that the amount of PTFE put down increases with deposition temperature and pressure. The XPS azimuthal angle dependence at low electron take-off angle is consistent with the aligned ribbon morphology. Azimuthal and polar angle dependence and charging studies show that hydrocarbon contamination observed in the XPS spectrum is located on top of the silicon wafer substrate, in the channels between the PTFE ribbons. Imaging XPS confirms the pressure dependence of PTFE coverage, and at low deposition pressure reveals tracks of PTFE ∼100 μm wide, aligned with the film draw direction. Together with the AFM data this leads to a description of PTFE transfer films as fractal materials.

Effect of Acetate Distribution on Surface Segregation in Poly(vinyl alcohol-co-vinyl acetate) Copolymer Films

The level of acetate-group surface segregation in poly(vinyl alcohol-co-vinyl acetate) (PVA−PVAc) films was found to depend markedly on the functional group distribution along the backbone (blockiness). PVA−PVAc polymers with both random and blocky distributions were prepared at levels between 2 and 12 mol % acetate and cast into films from aqueous solution. Films from polymers with blocky distributions showed significantly higher levels of acetate at the surface than in the bulk, while polymers with random distributions of acetate functionality exhibited little or no surface segregation. The level of acetate surface segregation was determined by both X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Blocky PVA−PVAc films containing 4 mol % were seen to have approximately 40 mol % PVAc at the outermost surface by XPS at low take-off angle. Bulk acetate levels and acetate group distributions were determined by NMR. Variations in the weight average molecular weight (Mw) between 40k and 155k, modifying the casting solvent, or annealing the films above Tg did not effect the level of surface segregation, suggesting that the segregation is not simply a kinetic phenomenon.

Chemical states of the molybdenum disilicide (MoSi2) surface

The analysis of the oxidation of MoSi2 at room temperature was carried out using X-ray photoelectron spectroscopy. A clean surface of MoSi2 was obtained by sputter-etching the bulk material inside the spectrometer, and the chemical states of the surface were examined with both high and low take-off angles for the conditions of as-etched and exposed to the air for different times. The commercially pure MoSi2 powder was also investigated in the as-received condition. The analysis indicated that the exposure of a clean molybdenum disilicide to the air for just a few minutes led to the formation of SiO2 and MoO2, and this oxidation would persist at least for more than 24 h with the final surface of MoSi2 being covered by a duplex oxide layer of SiO2 + MoO3.