Parity violation (PV) effects in chiral molecules have so far never been experimentally observed. To take up this challenge, a consortium of physicists, chemists, theoreticians, and spectroscopists has been established and aims at measuring PV energy differences between two enantiomers by using high-resolution laser spectroscopy. In this article, we present our common strategy to reach this goal, the progress accomplished in the diverse areas, and point out directions for future PV observations. The work of André Collet on bromochlorofluoromethane (1) enantiomers, their synthesis, and their chiral recognition by cryptophanes made feasible the first generation of experiments presented in this article.

Using a video-imaging technique, we characterized the effects of 8-isoprostaglandin F2α(8-iso-PGF2α) on retinal vasculature from piglets. 8-Iso-PGF2α potently contracted (EC50 = 5.9 ± 0.5 nM) retinal vessels. These effects were completely antagonized by the cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-12970, the thromboxane receptor antagonist L-670596, and the putative inhibitor of the non-voltage-dependent receptor-operated Ca2+ pathway SKF-96365; constrictor effects of 8-iso-PGF2α were also partly attenuated by the ETA-receptor blocker BQ-123 and an inhibitor of endothelin-converting enzyme, phosphoramidon, but was negligibly affected by the L-type voltage-gated Ca2+ channel blocker nifedipine. Correspondingly, 8-iso-PGF2αelicited endothelin release from retinal preparations, which was markedly reduced by SKF-96365. 8-Iso-PGF2α also increased thromboxane production in the retina and cultured endothelial cells, but not on retinovascular smooth muscle cells; these effects of 8-iso-PGF2α were blocked by indomethacin, CGS-12970, SKF-96365, and EGTA, but not by nifedipine. 8-Iso-PGF2α also increased Ca2+ transients in retinal endothelial cells, which were inhibited by SKF-96365 and EGTA, but not by nifedipine, whereas in smooth muscle cells U-46619, but not 8-iso-PGF2α, stimulated a rise in Ca2+ transients. Finally, H2O2+ FeCl2 (in vitro) and anoxia followed by reoxygenation (in vivo) stimulated formation of 8-iso-PGF2α in the retina. In conclusion, 8-iso-PGF2α-induced retinal vasoconstriction is mediated by cyclooxygenase-generated formation of thromboxane and, to a lesser extent, by endothelin after Ca2+ entry into cells, possibly through receptor-operated channels. Retinal vasoconstriction to 8-isoprostanes might play a role in the genesis of ischemic retinopathies.

Abstract-Historically, persons with paralysis have limited options for overground ambulation. Recently, powered exoskeletons, which are systems that translate the user's body movements to activate motors that move the lower limbs through a predetermined gait pattern, have become available. As part of an ongoing clinical study (NCT01454570), eight nonambulatory persons with paraplegia were trained to ambulate with a powered exoskeleton. Measurements of oxygen uptake (VO 2 ) and heart rate (HR) were recorded for 6 min each during each maneuver while sitting, standing, and walking. The average value of VO 2 during walking (11.2 +/-1.7 mL/kg/min) was significantly higher than for sitting and standing (3.5 +/-0.4 and 4.3 +/-0.9 mL/kg/min, respectively; p < 0.001). The HR response during walking was significantly greater than that of either sitting or standing (118 +/-21 vs 70 +/-10 and 81 +/-12 beats per minute, respectively; p < 0.001). Persons with paraplegia were able to ambulate efficiently using the powered exoskeleton for overground ambulation, providing the potential for functional gain and improved fitness.Clinical Trial Registration: ClinicalTrials.gov; NCT01454570; "The ReWalk Exoskeletal Walking System for Persons with Paraplegia (VA_ReWalk)"; https://clinicaltrials.gov/ct2/show/ NCT01454570

We introduce a constrained Monte Carlo method which allows us to traverse the phase space of a classical spin system while fixing the magnetization direction. Subsequently we show the method's capability to model the temperature dependence of magnetic anisotropy, and for bulk uniaxial and cubic anisotropies we recover the low-temperature Callen-Callen power laws in M .We also calculate the temperature scaling of the 2-ion anisotropy in L1 0 FePt, and recover the experimentally observed M 2.1 scaling. The method is newly applied to evaluate the temperaturedependent effective anisotropy in the presence of the Néel surface anisotropy in thin films with different easy axis configurations. In systems having different surface and bulk easy axes, we show the capability to model the temperature-induced reorientation transition. The intrinsic surface anisotropy is found to follow a linear temperature behavior in a large range of temperatures. PACS numbers: 75.30.Gw, 75.70.Rf, 75.10.Hk, 75.70.Ak Recently, the high temperature behavior of magnetic anisotropy has become important due to the applications in heat-assisted magnetic recording (HAMR) 5-7 . The idea of HAMR is based on the heating of the recording media to decrease the writing field of the high anisotropy media (such as FePt) to values compatible with the writing fields provided by conventional recording heads. Since the writing field is proportional to the anisotropy field H k = 2K eff u (T )/M(T ), the knowledge of the scaling behavior of the anisotropy K u with the magnetization M has become a paramount consideration for HAMR 8 . It should be noted that even in relatively simple systems, a simple scaling behavior predicted by the Callen-Callen theory is only valid at temperatures far from the Curie temperature. The systems proposed for HAMR applications can also include more complex composite media such as soft/hard bilayers 9 , FePt/FeRh with metamagnetic phase transition 10,11 , or exchange-bias systems 12 .The evaluation of the temperature dependence of magnetic anisotropy is also important for the modeling of the laser-induced demagnetization processes. The thermal decrease of the anisotropy during the laser-induced demagnetization has been shown to be responsi-

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A comprehensive analysis of the areal density potential of bit-patterned media recording shows that the recording performance is dominated by written-in errors. The statistical fluctuations of the magnetic properties and the locations of the individual bits lead to error probabilities so that some dots are either not recorded at all or cannot be recorded in the time window necessary to ensure synchronized writing. The highest areal densities are obtained with a combination of a pole head, a soft magnetic underlayer, and a storage medium of the composite type. Areal density scenarios of up to 5 Tbits/ in. 2 are analyzed.

Objective: To use vertical ground reaction force (vGRF) to show the magnitude and pattern of mechanical loading in persons with spinal cord injury (SCI) during powered exoskeleton-assisted walking.Research design: A cross-sectional study was performed to analyze vGRF during powered exoskeletonassisted walking (ReWalk™: Argo Medical Technologies, Inc, Marlborough, MA, USA) compared with vGRF of able-bodied gait. Setting: Veterans Affairs Medical Center. Participants: Six persons with thoracic motor-complete SCI (T1-T11 AIS A/B) and three age-, height-, weightand gender-matched able-bodied volunteers participated. Interventions: SCI participants were trained to ambulate over ground using a ReWalk™. vGRF was recorded using the F-Scan™ system (TekScan, Boston, MA, USA). Outcome measures: Peak stance average (PSA) was computed from vGRF and normalized across all participants by percent body weight. Peak vGRF was determined for heel strike, mid-stance, and toe-off. Relative linear impulse and harmonic analysis provided quantitative support for analysis of powered exoskeletal gait. Results: Participants with motor-complete SCI, ambulating independently with a ReWalk™, demonstrated mechanical loading magnitudes and patterns similar to able-bodied gait. Harmonic analysis of PSA profile by Fourier transform contrasted frequency of stance phase gait components between able-bodied and powered exoskeleton-assisted walking. Conclusion: Powered exoskeleton-assisted walking in persons with motor-complete SCI generated vGRF similar in magnitude and pattern to that of able-bodied walking. This suggests the potential for powered exoskeletonassisted walking to provide a mechanism for mechanical loading to the lower extremities. vGRF profile can be used to examine both magnitude of loading and gait mechanics of powered exoskeleton-assisted walking among participants of different weight, gait speed, and level of assist.

Background: Individuals with spinal cord injury (SCI) often use a wheelchair for mobility due to paralysis. Powered exoskeletalassisted walking (EAW) provides a modality for walking overground with crutches. Little is known about the EAW velocities and level of assistance (LOA) needed for these devices. Objective: The primary aim was to evaluate EAW velocity, number of sessions, and LOA and the relationships among them. The secondary aims were to report on safety and the qualitative analysis of gait and posture during EAW in a hospital setting. Methods: Twelve individuals with SCI ≥1.5 years who were wheelchair users participated. They wore a powered exoskeleton (ReWalk; ReWalk Robotics, Inc., Marlborough, MA) with Lofstrand crutches to complete 10-meter (10MWT) and 6-minute (6MWT) walk tests. LOA was defined as modified independence (MI), supervision (S), minimal assistance (Min), and moderate assistance (Mod). Best effort EAW velocity, LOA, and observational gait analysis were recorded. Results: Seven of 12 participants ambulated ≥0.40 m/s. Five participants walked with MI, 3 with S, 3 with Min, and 1 with Mod. Significant inverse relationships were noted between LOA and EAW velocity for both 6MWT (Z value = 2.63, Rho = 0.79, P = .0086) and 10MWT (Z value = 2.62, Rho = 0.79, P = .0088). There were 13 episodes of mild skin abrasions. MI and S groups ambulated with 2-point alternating crutch pattern, whereas the Min and Mod groups favored 3-point crutch gait. Conclusion: Seven of 12 individuals studied were able to ambulate at EAW velocities ≥0.40 m/s, which is a velocity that may be conducive to outdoor activity-related community ambulation. The ReWalk is a safe device for in-hospital ambulation.