Mass Measurements of Neutron-Deficient Yb Isotopes and Nuclear Structure at the Extreme Proton-Rich Side of the N=82 Shell.

High-accuracy mass measurements of neutron-deficient Yb isotopes have been performed at TRIUMF using TITAN's multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). For the first time, an MR-TOF-MS was used on line simultaneously as an isobar separator and as a mass spectrometer, extending the measurements to two isotopes further away from stability than otherwise possible. The ground state masses of ^{150,153}Yb and the excitation energy of ^{151}Yb^{m} were measured for the first time. As a result, the persistence of the N=82 shell with almost unmodified shell gap energies is established up to the proton drip line. Furthermore, the puzzling systematics of the h_{11/2}-excited isomeric states of the N=81 isotones are unraveled using state-of-the-art mean field calculations.

Effects of conditioning hops on drop jump and sprint performance: a randomized crossover pilot study in elite athletes.

BACKGROUND: It has previously been shown that conditioning activities consisting of repetitive hops have the potential to induce better drop jump (DJ) performance in recreationally active individuals. In the present pilot study, we investigated whether repetitive conditioning hops can also increase reactive jump and sprint performance in sprint-trained elite athletes competing at an international level. METHODS: Jump and sprint performances of 5 athletes were randomly assessed under 2 conditions. The control condition (CON) comprised 8 DJs and 4 trials of 30-m sprints. The intervention condition (HOP) consisted of 10 maximal repetitive two-legged hops that were conducted 10 s prior to each single DJ and sprint trial. DJ performance was analyzed using a one-dimensional ground reaction force plate. Step length (SL), contact time (CT), and sprint time (ST) during the 30-m sprints were recorded using an opto-electronic measurement system. RESULTS: Following the conditioning activity, DJ height and external DJ peak power were both significantly increased by 11 % compared to the control condition. All other variables did not show any significant differences between HOP and CON. CONCLUSIONS: In the present pilot study, we were able to demonstrate large improvements in DJ performance even in sprint-trained elite athletes following a conditioning activity consisting of maximal two-legged repetitive hops. This strengthens the hypothesis that plyometric conditioning exercises can induce performance enhancements in elite athletes that are even greater than those observed in recreationally active athletes.. In addition, it appears that the transfer of these effects to other stretch-shortening cycle activities is limited, as we did not observe any changes in sprint performance following the plyometric conditioning activity.

Identifying risk factors and proposing a risk-profile scoring scale for perioperative ischemic complications in carotid endarterectomies.

BACKGROUND: Carotid endarterectomy can reduce the risk of stroke in patients with severe symptomatic carotid artery stenosis, but the benefit of the procedure can be significantly influenced by the risk of perioperative ischemic complications. We conducted a retrospective study in order to assess the safety of the procedure in a low-volume single Neurosurgical Department and identify potential risk factors that are associated with the occurrence of a perioperative ischemic event. METHODS: The records of 218 procedures performed over a period of ten years were reviewed. The records were abstracted for demographics, neurologic history, degree of stenosis, comorbidities and ischemic complications within 30 days of surgery. RESULTS: The overall mortality was zero but 12 patients (5.5%) suffered from a perioperative ischemic event, half of which were non-reversible; four of them had a complete stroke and 2 an amaurosis. A postoperative ischemic complication was more likely for patients with a history of complete stroke (RR, 5.93; 95% CI, 1.7-23.0), contralateral vessel stenosis (RR, 11.6; 95% CI, 1.6-244.0), diabetes mellitus (RR: 3.3; 95% CI: 1.13-10.09), hypercholesterolemia (RR: 3.4; 95% CI: 1.13-10.44) and hypertriglyceridemia (RR: 4.6; 95% CI: 1.31-12.42). Using these factors we created a scoring system that stratifies patients into low, medium and high risk. All but two of the patients with perioperative ischemic events fall into the high risk group. Patients with the aforementioned risk factors may have an elevated risk of adverse outcomes. CONCLUSIONS: Carotid endarterectomies can be performed with exceptional safety in low-volume-centers, but patients with a history of stroke, contralateral internal carotid artery stenosis and three or more atherosclerotic factors are at a higher risk of perioperative ischemic complications. Our scoring system could prove a valuable tool when weighting the risk-to-benefit ratio for an individual patient.

Differential modulation of motor cortex plasticity in skill- and endurance-trained athletes.

PURPOSE: Extensive evidence exists that regular physical exercise offers neuroplastic benefits to the brain. In this study, exercise-specific effects on motor cortex plasticity were compared between 15 skilled and 15 endurance trained athletes and 8 controls. METHODS: Plasticity was tested with a paired associative stimulation (PAS) protocol. PAS is a non-invasive stimulation method developed to induce bidirectional changes in the excitability of the cortical projections to the target muscles. Motor cortex excitability was assessed by motor-evoked potentials (MEPs) in the task-relevant soleus muscle, elicited with transcranial magnetic stimulation, before and following PAS. To test for changes at the spinal level, soleus short latency stretch reflexes (SLSR) were elicited before and after PAS. RESULTS: PAS induced a significant (76 ± 83 %) increase in MEP amplitude in the skill group, without significant changes in the endurance (-7 ± 35 %) or control groups (21 ± 30 %). Baseline MEP/post MEP ratio was significantly different between the skill and endurance groups. SLSR remained unchanged after the PAS intervention. CONCLUSION: The possible reason for differential motor cortex plasticity in skill and endurance groups is likely related to the different training-induced adaptations. The findings of the current study suggest that long-term skill training by skill group induced preferable adaptations in the task-related areas of the motor cortex because increased plasticity is known to enhance motor learning.

Repetitive hops induce postactivation potentiation in triceps surae as well as an increase in the jump height of subsequent maximal drop jumps.

Postactivation potentiation (PAP) has been defined as the increase in twitch torque after a conditioning contraction. The present study aimed to investigate the effectiveness of hops as conditioning contractions to induce PAP and increase performance in subsequent maximal drop jumps. In addition, we wanted to test if and how PAP can contribute to increases in drop jump rebound height. Twelve participants performed 10 maximal two-legged hops as conditioning contractions. Twitch peak torques of triceps surae muscles were recorded before and after the conditioning hops. Then, subjects performed drop jumps with and without 10 conditioning hops before each drop jump. Recordings included ground reaction forces, ankle and knee angles and electromyographic activity in five leg muscles. In addition, efferent motoneuronal output during ground contact was estimated with V-wave stimulation. The analyses showed that after the conditioning hops, twitch peak torques of triceps surae muscles were 32% higher compared to baseline values (P < 0.01). Drop jumps performed after conditioning hops were significantly higher (12%, P < 0.05), but V-waves and EMG activity remained unchanged. The amount of PAP and the change in drop jump rebound height were positively correlated (r(2) = 0.26, P < 0.05). These results provide evidence for PAP in triceps surae muscles induced by a bout of hops and indicate that PAP can contribute to the observed performance enhancements in subsequent drop jumps. The lack of change in EMG activity and V-wave amplitude suggests that the underlying mechanisms are more likely intramuscular than neural in origin.