Detection of CMB-Cluster Lensing using Polarization Data from SPTpol.

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg^{2} survey at the locations of roughly 18 000 clusters with richness λ≥10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8σ. The mean stacked mass of the selected sample is found to be (1.43±0.40)×10^{14}M_{⊙} which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.

Increased variability in finger position occurs throughout overarm throws made by cerebellar and unskilled subjects.

We investigated the ability of cerebellar patients and unskilled subjects to control finger grip position and the amplitude of finger opening during a multijoint overarm throw. This situation is of interest because the appropriate finger control requires predicting the magnitude of back forces from the ball on the finger throughout the throw and generating the appropriate level and rate of change of finger flexor torque to oppose the back force. Cerebellar patients, matched controls, and unskilled subjects threw tennis balls and tennis-sized balls of different weights. In all cases angular positions of five arm segments in three dimension were recorded at 1,000 Hz with the search-coil technique as subjects threw from a seated position. When the hand was stationary, cerebellar patients showed a normal ability to grip the ball and open the fingers and drop the ball. In contrast, in overarm throws where a back force occurred on the fingers, cerebellar patients showed an abnormally large variability in amplitude of the change in finger position when gripping, in amplitude of finger opening, and in amplitude of the change in finger position 10 ms after ball release. This was not due to more trial-to-trial variation in throwing speed. When throwing balls of increasing weights, both controls and cerebellar patients had increasing finger flexions after ball release that indicated that, on average, both scaled finger force in proportion to ball weight during the throw. Unlike skilled controls, cerebellar patients showed a small (<20 degrees ) increase in the amplitude of finger opening with balls of increasing weight. However, neither the increase in variability of finger position nor the increase in finger amplitude with balls of increasing weight were unique cerebellar signs because both were observed to various degrees in unskilled throwers. It is concluded that in the absence of either normal cerebellar function or skill, the central neural activity that controls finger opening in throwing can increase finger flexor force to oppose an increase in back force from heavier balls and can open the fingers but cannot control finger force or finger opening precisely and consistently from throw to throw. These results fit with the idea that cerebellar disorders are greater in multijoint than single-joint movements because control of force is more complicated. They are also consistent with the hypothesis that the cerebellum produces skill in movement by reducing variability in the timing and force of muscle contractions.