Kinetic-Energy- and Angular-Resolved Fragmentation of CO in Vibrational-Resolved C 1s Excitation

Angular distributions of C++O+ from CO were measured, following vibrationally resolved C 1s excitations into the 2pπ, 3sσ, and 3pπ orbitals as well as into higher unresolved orbitals. A time-of-flight mass spectrometer, with a multihit-type position-sensitive anode, was used for the measurements. The anisotropy parameters (β) of C++O+ approach their theoretically expected values as the released kinetic energy in the fragmentation increases. The value of the β parameters remains constant for all vibrational states within each orbital

Electric-octupole and pure-electric-quadrupole effects in soft-x-ray photoemission

Second-order [O(k^2), k=omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and theoretical study of angular distributions of neon valence photoelectrons in the 100--1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms. Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.Comment: 4 pages, 3 figure

Vibrational-State-Dependent Decay of the CO C(1s) Excitation

Molecular ionization and ionic fragmentation of core excited CO valence and Rydberg states are studied by partial-ion-yield spectroscopy at vibrational resolution. The vibrational intensities of the Rydberg excitations differ significantly depending on the ionization and/or fragmentation channel. The observed intensity variations are explained by nondissociative excited final ionic states of the subsequent molecular Auger decay. The vibrational levels of these final states become selectively depopulated due to interaction with dissociative decay channels leading to ionic fragmentation

Matching triceps surae muscle strength and tendon stiffness eliminates age-related differences in drop-jump performance

INTRODUCTION: Age-related changes in locomotor performance and motor task execution strategy have been associated with reduced leg-extensor muscle-tendon unit capacities in old age (Karamanidis & Arampatzis, 2005; Kulmala et al., 2014). However, it remains unclear if leg-extensor muscle strength and tendon stiffness are the primary drivers of these alterations seen with ageing, or if other factors also play a role. We aimed to determine if potential age-related differences in drop jump (DJ) performance and motor task execution strategy would be eliminated in a group of younger and middle-aged adults when triceps surae (TS) muscle strength and Achilles tendon (AT) stiffness were matched. METHODS: Ankle plantarflexion moments and AT stiffness of both legs were assessed in 12 younger (20-30y) and 12 middle-aged (50-65y) adults during isometric plantarflexion contractions using dynamometry and ultrasonography synchronously. Tendon elongation during the loading phase was assessed by visualising the myotendinous junction of the gastrocnemius medialis muscle and stiffness of the AT was determined in the linear region of the force-length relationship. There were no significant differences between the matched young and middle-aged adults in maximal ankle plantarflexion moment (young: 3.2±0.4; middle-aged: 3.1±0.5 Nm/kg) and AT stiffness (580.3±121.8 vs. 590.2±108.4 N/mm). On a second occasion, the matched participants performed a series of DJs from different starting heights (13, 23, 33 and 39 cm) onto a force plate. A two-way ANOVA (factors: age, starting height) was performed in order to detect any age or starting height effects on DJ height and motor task execution strategy. The effect of TS muscle strength and AT stiffness on DJ height was investigated by using Pearson’s product-moment correlation coefficient. RESULTS: There was no significant age effect for DJ performance, meaning that matched younger and middle-aged adults achieved similar DJ heights, independent of starting height (Fig. 1). Concerning DJ mechanics, there were significant age effects (p<.05) on ground contact time, maximum vertical ground reaction force and mechanical power, with the middle-aged adults showing higher ground contact times (Fig. 2A), but lower forces (Fig. 2B) and lower mechanical power (Fig. 2C) for all starting heights. Significant correlations were found between DJ performance and TS muscle strength and AT stiffness (.41≤r≤.81; p<.05) for all starting heights. DISCUSSION: The results of the current study demonstrate that matching younger and middle-aged adults for TS muscle strength and AT stiffness eliminates age-related differences in the performance of a jumping task, independent of starting height and hence, task demand. However, the age groups used different motor task execution strategies, as measured by ground contact time, ground reaction forces and mechanical power for all starting heights, indicating that while changes in leg extensor muscle strength and tendon stiffness may be the primary drivers of deteriorated locomotor performance in older age, they may not be major contributors to motor task execution strategy during jumping. CONCLUSION: Jumping performance appears to be unaffected when leg extensor muscle strength and tendon stiffness are maintained with age and therefore, countering the degeneration of these properties may help prevent the decline in locomotor performance seen with ageing. REFERENCES: Karamanidis, K., & Arampatzis, A. (2005). Mechanical and morphological properties of different muscle-tendon units in the lower extremity and running mechanics: effect of aging and physical activity. The Journal of Experimental Biology, 208, 3907–23. Kulmala, J.-P., Korhonen, M. T., Kuitunen, S., Suominen, H., Heinonen, A., Mikkola, A., & Avela, J. (2014). Which muscles compromise human locomotor performance with age? Journal of The Royal Society Interface, 11, 20140858

Full Multiple Scattering Analysis of XANES at the Cd L 3- and O K- Edges in CdO Films Combined with a Soft-X-Ray Emission Investigation

X-ray absorption near edge structure (XANES) at the cadmium L3 and oxygen K edges for CdO thin films grown by pulsed laser deposition method, is interpreted within the real-space multiple scattering formalism, FEFF code. The features in the experimental spectra are well reproduced by calculations for a cluster of about six and ten coordination shells around the absorber for L3 edge of Cd and K edge of O, respectively. The calculated projected electronic density of states is found to be in good agreement with unoccupied electronic states in experimental data and allows to conclude that the orbital character of the lowest energy of the conductive band is Cd 5s-O 2p[sigma]*. The charge transfer has been quantified and not purely ionic bonding has been found. Combined XANES and resonant inelastic x-ray scattering measurements allow us to determine the direct and indirect band gap of investigated CdO films to be ~2.4 eV and ~0.9 eV, respectively

Age-related differences in drop-jump performance are eliminated by matching triceps surae muscle strength and Achilles tendon stiffness.

INTRODUCTION Reduced leg-extensor muscle strength and tendon stiffness in old age have been associated with changes in locomotor performance and motor task execution strategy (Karamanidis and Arampatzis, 2005; Kulmala et al., 2014). However, if leg-extensor muscle-tendon unit (MTU) mechanical properties are the only primary drivers of these alterations seen with ageing remains unclear. Therefore, we examined if matching triceps surae (TS) muscle strength and Achilles tendon (AT) stiffness eliminates potential age-related differences in drop jump (DJ) performance and motor task execution strategy in younger and middle-aged adults

Matching participants for triceps surae mechanical properties eliminates age-related differences in drop jump performance

Introduction Age-related declines in locomotor performance have been associated with a degeneration of the triceps surae muscle-tendon unit (MTU) capacities (Kulmala et al., 2014). However, to our knowledge, no studies have compared the motor task performance of young and older adults with similar triceps surae muscle strength and Achilles tendon stiffness. In the current study, we aimed to determine if differences in drop jump height or motor task execution strategy between young and middle-aged adults exist, when triceps surae MTU capacities (muscle strength and tendon stiffness) were matched. Methods The triceps surae MTU biomechanical properties of 29 middle-aged (50 - 65 years) and 26 younger (20 - 30 years) adults were assessed during isometric voluntary ankle plantarflexion contractions of the dominant leg using a custom-made dynamometer and ultrasonography (27 Hz; MyLabTMOne, Esaote; Genua, Italy) simultaneously. The resultant joint moments were calculated by means of inverse dynamics. The elongation of the tendon during contraction was assessed by digitizing the myotendinous junction of the gastrocnemius medialis muscle with a custom-made Matlab software (Matlab 2013b, MathWorks Inc., Natick, Massachusetts, USA) while taking into account the effect of potential ankle joint angular rotation during contraction (Muramatsu et al. 2001). Tendon stiffness was determined in the linear region of the force-length relationship. Following the MTU measurements, the 12 young adults with the lowest triceps surae muscle strength and the 12 middle-aged adults with the greatest muscle strength were compared. There were no significant differences between the matched young and middle-aged adults in muscle strength (young: 3.2 ± 0.4; middle-aged: 3.1 ± 0.5 Nm/kg), tendon stiffness (580.3 ± 121.8; 590.2 ± 108.4 N/mm) or tendon energy storage capacity (217 ± 63.2; 187.5 ± 82.7 J). The matched participants then completed a series of drop jumps. The instructions given to the subjects were “jump as high as possible with as little knee flexion as possible”. In order to analyse drop jump performance and motor task execution strategy, ground contact time, average vertical ground reaction force, average mechanical power and jumping height were determined during drop jumps from different heights (13, 23, 33 and 39 cm) onto a force plate (90 x 60 cm, 1000 Hz; Kistler, Winterthur, CH). A two-way repeated measures ANOVA with age and drop height as factors was conducted in order to detect age-related differences in drop jump height and motor task execution strategy. The effect of muscle strength and tendon stiffness on drop jump height was investigated using Pearson’s product-moment correlation coefficient. Results Younger and middle-aged adults attained comparable jumping heights independent of the drop jump height (Fig. 1). There were significant age effects on ground contact time (p < .01) and average vertical ground reaction force during ground contact phase (p < .01) (Fig. 1), with the middle-aged adults showing higher ground contact times but lower forces than the younger adults, leading to a significant age effect on mechanical power (p < .05). Significant (p < .05) correlations were found between triceps surae MTU capacities and drop jump height (.41 ≤ r ≤ .81; p < .05). Discussion The results of the current study demonstrate that when triceps surae MTU capacities are matched, young and middle-aged adults show comparable performance (jump height) of a jumping task. However, the motor strategies used to achieve these similar performances differ, with the middle-aged adults demonstrating longer ground contact times, lower ground reaction forces and hence lower average mechanical power. Muscle strength and tendon stiffness appear to play an important role in jumping performance and countering the degeneration of these properties may help prevent the decline in locomotor function seen with ageing. Finally, the results suggest that neuromuscular factors other than maximum isometric strength and tendon stiffness may influence motor task execution strategy during jumping, such as the power generating capacity of the triceps surae muscle. References Kulmala, J. P., Korhonen, M. T., Kuitunen, S., Suominen, H., Heinonen, A., Mikkola, A. et al. (2014). Which muscles compromise human locomotor performance with age? Journal of The Royal Society Interface, 11, 20140858. Muramatsu, T., Muraoka, T., Takeshita, D., Kawakami, Y., Hirano, Y. & Fukunaga, T. (2001). Mechanical properties of tendon and aponeurosis of human gastrocnemius muscle in vivo. Journal of Applied Physiology (1985), 90, 1671-1678

Matching Participants for Triceps Surae Muscle Strength and Tendon Stiffness Does Not Eliminate Age-Related Differences in Mechanical Power Output During Jumping

Reductions in muscular power output and performance during multi-joint motor tasks with aging have often been associated with muscle weakness. This study aimed to examine if matching younger and middle-aged adults for triceps surae (TS) muscle strength and tendon stiffness eliminates age-related differences in muscular power production during drop jump. The maximal ankle plantar flexion moment and gastrocnemius medialis tendon stiffness of 29 middle-aged (40–67 years) and 26 younger (18–30 years) healthy physically active male adults were assessed during isometric voluntary ankle plantar flexion contractions using simultaneous dynamometry and ultrasonography. The elongation of the tendon during the loading phase was assessed by digitizing the myotendinous junction of the gastrocnemius medialis muscle. Eight younger (23 ± 3 years) and eight middle-aged (54 ± 7 years) adults from the larger subject pool were matched for TS muscle strength and tendon stiffness (plantar flexion moment young: 3.1 ± 0.4 Nm/kg; middle-aged: 3.2 ± 0.5 Nm/kg; tendon stiffness: 553 ± 97 vs. 572 ± 100 N/mm) and then performed series of drop jumps from different box heights (13, 23, 33, and 39 cm) onto a force plate (sampling frequency 1000 Hz). The matched young and middle-aged adults showed similar drop jump heights for all conditions (from lowest to highest box height: 18.0 ± 3.7 vs. 19.7 ± 4.8 cm; 22.6 ± 4.2 vs. 22.9 ± 4.9 cm; 24.8 ± 3.8 vs. 23.5 ± 4.9 cm; 25.2 ± 6.2 vs. 22.7 ± 5.0 cm). However, middle-aged adults showed longer ground contact times (on average 36%), lower vertical ground reaction forces (36%) and hence lower average mechanical power (from lowest to highest box height: 2266 ± 563 vs. 1498 ± 545 W; 3563 ± 774 vs. 2222 ± 320 W; 4360 ± 658 vs. 2475 ± 528 W; 5008 ± 919 vs. 3034 ± 435 W) independent of box height. Further, leg stiffness was lower (48%) in middle-aged compared to younger adults for all jumping conditions and we found significant correlations between average mechanical power and leg stiffness (0.70 ≤ r ≤ 0.83; p < 0.01). Thus, while jumping performance appears to be unaffected when leg extensor muscle strength and tendon stiffness are maintained, the reduced muscular power output during lower limb multi-joint tasks seen with aging may be due to age-related changes in motor task execution strategy rather than due to muscle weakness

Nondipole Effects in the Photoionization of Xe 4d5/2 and 4d3/2: Evidence for Quadrupole Satellites

Measurements of nondipole parameters in spin-orbit-resolved Xe 4d photoionization demonstrate dynamical differences arising from relativistic effects. The experimental data do not agree with relativistic random-phase approximation calculations of single ionization dipole and quadrupole channels. It is suggested that the discrepancy is due to the omission of multiple-excitation quadrupole channels, i.e., quadrupole satellite transitions

Non-Dipolar Electron Angular Distributions from Fixed-in-Space Molecules

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N2. Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame